BMW Reihe "/2" (1955-1969)

Dokument "BMW /2"


BMW-Veteranen - Allgemeines




Fragen und mögliche Themen für Kauf und Restauration

Diese Liste ist sicher nicht vollständig! Aber irgendwann muß man ja mal anfangen...


/2 Motor zerlegen

Das folgende ist auch schon ohne Text aussagekräftig.

Der Patient auf dem OP-Tisch:

Roter Kreis: Ölrücklauf

Alte Kolben haben so ein "Spannband" innen:

"Ed Korn's Universalwerkzeug" im Einsatz:

Hier die anderen Teile dieses Werkzeugs:

Die Ölpumpe - das ist alles, was ein Wälzlagermotor braucht, denn man hat sich ansonsten die Fliehkraft zunutze gemacht:

Blick auf das vordere Ölschleuderblech:

Durch diese Öffnung im vorderen Ölschleuderblech wird das Schleuderöl in den Pleuellagerbolzen der Kurbelwelle geleitet - Schmierung allein durch Fliehkraft. (Genauso sieht es an der anderen, hinteren KW-Seite aus für das andere, rechte Pleuellager.)

So sollte es nicht aussehen:

Im Pleuellagerbolzen hat es 2 Bohrungen, durch die das Schleuderöl auf die unteren Pleuellager (Wälzlager) gelangt. Wenn diese durch Schmutz verstopft werden, der die Rillen der Ölschleuderbleche zum Überlaufen bringt ...


Hier hat jemand tiefgreifend umgerüstet:

hinten das Doppelpendellager:

this SKF toroidal bearing represents the most exciting recent development in bearing technolgy - an engineers dream! SKF has a patent on this and I was lucky - they make a size that fits... sort of. This bearing eliminates all axial creeping of the 2 journal seats. The continuous expansion and contraction of the housing versus the crank is one reason for wear in the journal seats when ball bearings are used. The only axial pressures remaining are from the helical cam gears (minimal) and the clutch actuator. Both are taken up by the very capable spherical double row roller bearing at front. I have left out the third bearing near the generator as it's weight has dissapeared (see 'Electrics) and as it would disturb the now perfectly determined system.

SKF toroidal bearing is 7 mm longer than the OEM one. This required the flywheel cone to be shortened (while is was on the lathe I asked the machinist to lighten it - see the markings). Because the toroidal bearing can have its races offset axially, there is no need for the spacer between the inner race and the slinger. This saved a bit in length and allowed the flywheel cone machined back by only 4mm. The Viton seal at the back of the crank case just fitted flush with the bearing carrier. Lucky. Punch marks on the crank idicate that crank has been apart. The alignment however wasn't perfect.

/2 FAQ

Date: Fri Mar 24 07:41:07 1995
From: (kees van der heiden)

Rotterdam, 21-10-1994

This is my attempt for a /2 FAQ. Because I'm in the middle of the res-
toration of a '58 R69, I'm very interested in these bikes, and still have
vivid memories about all the problem area's. So I collected any usefull
information that I could get, asked around for more info, and put it all
together. This is the result. Don't look too hard at all the grammatical
errors, English is not my native tongue. But when you find any error, lie
or misconception in the contents don't hesitate to flame ahead.

My email adress:
- Some History
- Technical data
- More technical data
- Problem areas
- Special tools
- Sidecars
- Magnetos

The /2 range of BMW's motorcycles is usually regarded to be the swingarm
models, build from 1955 - 1960. In fact this term '/2' isn't quite correct,
because only the modelnames of the R50 and R60 from '60 -'69 had this
extension. But, what's in a name?

Some history:
After the second world war, The German motorcycle manufacturers weren't
allowed to build engines with more than 250cc displacement. The BMW plant
was heavily bombed, so they were rather late with their first postwar bike,
the R24. Not the famous boxer engine, but a very modest single. Nonetheless
it was a huge succes, and allowed BMW to make enough profit for their first
postwar boxer, after the restrictions were relaxed. This bike the R51/2 made
from 1950 - 1951 was nearly the same as the prewar R51. The bike had a
twin tube frame with plunger rear suspension and a telescopic frontfork. It
had an engine with two camshafts, driven by a chain, wich allowed short
In 1951 the new boxers were introduced, the R51/3 and the R67, and the R68,
the first BMW 100 mph runner, followed in 1952. These had a new engine in
virtually the same old frame. This engine is of interest to us, because
it is the same as used in the '/2' series until 1969, with detail
modifications of course. This engine featured one camshaft, driven
by helical cut gears. A magneto on front of the camshaft, a DC dynamo on
front of the crankshaft and the oilpump on an extra gear under the crank-
shaft. All shafts had very big ball bearings. The big ends ran on needle
bearings, and the small end had to do with a bronse bush. This layout was
retained until 1969, with the excepton of the rear crankshaft bearing
on the bigger, more powerfull machines, which had a swival joint bearing to
cope with crankshaft flexing.
The cylinder was cast iron. The piston and cylinder head were made from
light metal. At the back of the engine a large flywheel was attached to
the crankshaft, wich incorporated the car type single plate dry clutch.

In 1955 was the introduction of the R50 and the R69. They had the new
frame but the old engines. The new frame was a sensation in these days.
It was very comfortable and had good road holding properties. At the back
was a swing arm, at last universally regarded as the optimum configuration
for the rear end of a bike. The mainframe still had the same style as the
old plunger frame, with neat loops next to the rear wheel and rather
strange extensions to hold the rear suspension units. The front was very
exotic. Here was a swing arm , according to the Earless patent. This was
a very hot item, mainly used on racers, and on some fancy street bikes.
But these latter weren't always a succes, because of their flimsy layout.
BMW did it better. They made a very strong fork from conical tube and
used conical roller bearings to carry the swing arm. They used the same
bearings in the rear swingarm.

Also the gearbox was changed in 1955. The previous models had a two-shaft
gearbox, but these newer boxes had tree shafts. The consequence was a change
of turning direction in the cardan. This was dealed with by changing the
position of the pignon wheel in the rearwheel.

The introduction of the sportsmodels R50S and R69S, started some big
difficulties. The engines had a lot of reliability problems, like
broken crankshafts, cylinderhead failures and even teared off cylinders.
The crankshaft was too flexible for these kind of power outputs. The
R50S was discontinued in 1962 after only 1634 units produced. The R69S
got a vibration damper on the crankshaft in front of the dynamo. These
engines are recognized by the extra bump on the front cover. The R69S also
got a hydraulic steering damper to cope with the high speed instability.

At the very end, since 1967, the US models were available with a tele-
scopic frontfork, as develloped for the /5 BMW's. This model was only
available in the USA, and German customers were rather sauer about this.
They had to wait until the introduction of the /5 range.

The development of the single cylinder models was a bit different. After
the R24 without rear suspension, came the R25 with a plunger frame, like
the R51/3, but smaller and cheaper manufactured. Although the R25 and
its succesors the R25/2 and /3 sold in huge quantities, the factory didn't
spend as much development effort in these bikes as in the boxers. There
were some thermical problems that were dealt with in the cheapest way, by
painting the cylinderhead black. Later the heads had much larger cooling fins,
and thus the engine was used in the R26.

The engine was quite different from the boxer engines. It also had a
longitudinal crankshaft, but the camshaft was driven by a chain. It
also hadn't a magneto, but it had to do with coil ignition.

The frame of the R26 and R27 strongly resembles the frame of the R50 etc.
In fact it has completely the same Earless frontfork, of course with
different shoch absorbers and springs. The differences are at the backside.
The reinforcement bars near the swingarm bearings are different, and the
suspension units are more slanted. The 'cardan' of the single cylinder
models also hasn't a cardan coupling, instead it still has the Hardy
coupling. This is a disk of woven fabric, which allows some up and down
The R27 has the very special rubber engine mountings. BMW had investigated
this subject intensily. Because the R26 had quite a lot of power, the
vibrations were very strong. This was not only very uncomfortable, but it
also inflicted the reliability. These rubber mountings lessened the degree
of vibration to a very acceptable amount, although the power output was
raised from 15 to 18 hp.

Technical details:
Model           R50 (/2)    | R50S    | R60 (/2)    | R69      | R69/S   | R26     | R27
Period          '55-'60('69)| '60-'62 | '56-'60('69)| '55-'60  | '60-'69 | '56-'60 | '60-'66
Cylinders       2 in boxer layout                                       | 1 vertical
Bore and stroke 68x68 mm              | 72x73 mm                         | 68x68
Displacement    494 cc                | 594 cc                           | 247 cc
Valves          2 / cylinder  ohv
Compresion      6.8:1       | 9.2:1   | 6.5:1 (7.5) | 7.5:1    | 9.5:1   | 7.5:1   | 8.2:1
Horsepower      26          | 35      | 28 (30)     | 35       | 42      | 15      | 18
At rpm          5800        | 7650    | 5600 (5800) | 6800     | 7000    | 6400    | 7400
Carburettor     Bing 24mm   | 26mm    | 24mm        | 26mm     | 26mm    |  26mm   | 26mm
Electrics       Norris magneto and Bosch DC generator 60-90W 6V          | Norris coil ignition
Clutch          Single dry plate
Gearbox         4 speed, foot operated
Frame           Twin tube
Suspension      Swing arm front and rear. Boge shock absorbers.
Tires           3.50 x 18                                                | 3.25x18
Brakes          Fullwidth 200mm drumbrakes. Duplex front                 | Fullw. 160mm drum
Length          2125 mm                                                  | 2090 mm
Width           660 mm                                                   | 660 mm
Height          725 mm                                                   | 770 mm
Tank            17 l                                                     | 15 l
Weight          195 kg      | 198 kg  | 195(198) kg | 202 kg   | 202 kg  | 158 kg  | 162 kg
Topspeed km/h   140         | 160     | 145 (150)   | 165      | 175     | 128     | 130
Production      13510(19036)| 1634    | 3530(17306) | 2956     | 11317   | 30236   | 15364
Newprice  DM    3050,-      | 3535,-  | 3235(3315),-| 3950,-   | 4030,-  | 2150,-  | 2430,-


Motorcycle Model             R50      R50S     R60(/2)  R69S      R69


Type of Engine               four-cycle, with V-type overhead valves
Nominal rated hp  (DIN)      26       35       28(30)   42        35
at engine r.p.m.             5,800    7,650    5,600    7,000     6800
No. of cylinders             2        2        2        2         2
Cylinder arrangement         horizontally opposed
Bore (mm.)                   68       68       72       72        72
Stroke (mm.)                 68       68       73       73        73
Piston displacement (c.c.)   490      490      590      590       590
Compression ratio            6.8:1    9.2:1    6.5:1    9.5:1     7.5:1
Valve timing, with valve clearance of .08" (2mm), (tolerance +-2.5 deg)
Intake opens                 6 deg.   4 deg.   6 deg.   4 deg.    3.5 deg
			     after    after    after    after     before
			     T.D.C.   T.D.C.   T.D.C.   T.D.C.    T.D.C.
Intake closes                34 deg.  44 deg.  34 deg.  44 deg.   43.5 deg
			     after    after    after    after     after
			     B.D.C.   B.D.C.   B.D.C.   B.D.C.    B.D.C
Exhaust opens                34 deg.  44 deg.  34 deg.  44 deg.   43.5 deg
			     before   before   before   before    before
			     B.D.C.   B.D.C.   B.D.C.   B.D.C.    B.D.C.
Exhaust closes               6 deg.   4 deg.   6 deg.   4 deg.    3.5 deg
			     before   before   before   before    after
			     T.D.C.   T.D.C.   T.D.C.   T.D.C.    T.D.C
Valve clearance (as measured when engine is cold):
Intake                       .006"    .006"    .006"    .006"     .006-.008"
			    (.15mm)  (.15mm)  (.15mm)  (.15mm)   (.15-.20mm)
Exhaust                      .008"    .008"    .008"    .008"     .008-.009"
			    (.20mm)  (.20mm)  (.20mm)  (.20mm)   (.20-.25mm)
Lubrication system           combined force-feed/centrifugal lubrication,
			     operated by geared pump; oil sump.

Carburetors             R50            R50S           R60(/2)        R69S            R69

Type                    two inclined BING carburetors with sliding throttle
			and needle valve
BING model      left    1/24/45        1/26/71        1/24/95(125)   1/26/69         1/26/10
		right   1/24/46        1/26/72        1/24/96(126)   1/26/70         1/26/9
Carburetor passage      .94" (24mm)    1.02" (26mm)   .94" (24mm)    1.02" (26mm)    1.02" (26mm)
Main jet                105            135            105(110)       135             115
Needle jet 45-251/      1308           1208           1208(1308)     2108            1208
Jet needle              46-255         46-934, No. 4  1467(46-255)   46-934, No. 4   No. 4
Needle position         3              2              3              2               1
Idling jet              35             35             35             35              35
Idling mixture adjusting
screw   proper position: open 1 to 2 1/2 turns
Sliding throttle        22-470         22-531         22-470         22-531          -
Weight of float         1/4 oz (7g)    1/4 oz (7g)    1/4 oz (7g)    1/4 oz (7g)     1/4 oz (7g)
Intake air filter       common micronic dry filter; with choke for R50, R60 and R69
			without choke for R50S and R69S.

Electrical equipment

Ignition                BOSCH MZ ad/R magneto
Drive                   direct from camshaft, at half engine speed
Contact breaker gap     .016" (.4mm)
Ignition timing         automatic centrifugal advance and retard unit on camshaft
			(+ manual advance on R69)
Firing point            9 deg. before T.D.C.   (2 deg on R69)
			(with governor weights in stationary position)
			(with manual on retard on R69)
Timing range            30 deg. of crankshaft  (30+10 deg. on R69)
Max. advance            39+-2 deg. before T.D.C. (42 before T.D.C. on R69)

Spark plugs

R50,R60 and R69         BOSCH W240 T1, or BERU 240/14
R50S and R69S           for running-in period: BOSCH W240 T1, or BERU 240/14;
			afterwards: BOSCH W260 T1, or BERU 260/14
Electrode gap           .024" (.6mm)

Generator (dynamo)      BOSCH LJ/CGE 60/6/1700 R 5, with integral voltage regulator
Drive                   direct from camshaft
Horn                    BOSCH HO/FDG 6/1, or KLAXON ETF/4 D

Lighting System

Headlights                  BOSCH LE/MTA 160x2 (48/3)
Bulb data
Country and traffic beam    Bilux lamp (twin-filament), 6 V, 35/35 watts
Parking light               pilot lamp, 6V 2 watts
Neutral indicator           pilot lamp, 6V 2 watts
Charging indicator          pilot lamp, 6V 2 watts
Speedometer illumination    pilot lamp, 6V 2 watts
Taillight and stoplight     twin-filament lamp, 6V 5/18 watts
License plate illumination  round bulb lamp, 6V, 5 watts
Blinker unit                HELLA BI 81
Blinker bulb                tubular lamp, 6V, 18 watts
Jack (socket), one pole under saddle; for sidecar lighting or flashlight


Clutch                        single-plate dry clutch with diaphragm spring
Transmission                  four-speed, with sliding dog clutches, integral
			      with engine, torque-dampened in all gears
Gear shift                    positive-stop, sequential, foot-operated
Gear ratios                                    R50 and R60 with sidecar
1st                           4.171:1                 5.33:1
2nd                           2.725:1                 5.02:1
3rd                           1.938:1                 2.04:1
4th                           1.54:1                  1.54:1
Power transmission from       fully enclosed universal shaft in right-hand rear
gearbox to rear wheel         swinging arm; axle drive by spiral bevel gears
Bevel gear ratios             R50, R60      R50S          R69S          R69
Solo                          3.13:1        3.58:1        3.13:1        3.18:1
No. of teeth                  8/25          7/25          8/25          11/35
Sidecar                       4.33:1        (4.33:1       (4.33:1       4.33:1
No.of teeth                   6/26          6/26)         6/26)         6/25)

Frame, Suspension, Wheels

Frame           welded duplex-tube steel frame
Suspension      pivoted swinging arms with hydraulically dampened suspension
		units and dual action hydraulic shock absorbers
Brakes          light-alloy full-hub brakes with integral gray-cast iron rings
		brake drum diam. 7.8" (200mm); width 1.4" (35mm)
		effective brake lining area 28.2 sq. in. (182 cm3)
		front: duplex brake (2 leading shoes)
		rear: simplex brake
Solo            chromed steel drop-center rims, 2.15Bx18 (40 spokes)
		or painted steel, or high shoulder aluminium rims.
Sidecar         all wheels : chromed steel drop-center rims; front 2.15Bx18,
			     rear 2.75Cx18
Tires                   R50       R50S        R60       R69S       R69
Solo                    3.50x18   3.50x18S    3.50x18   3.50x18S   3.50x18S
Rear, with sidecar      4.00x18   (4.00x18)   4.00x18   (4.00x18)  (4.00x18)
Max. unbalance          .32 oz (9 g), as measured at inner rim diameter

Tire Pressures                  Front Wheel     Rear Wheel      Sidecar Wheel
Driver alone                    24 psi          28 psi          -
				1.7 kg/cm3      2.0 kg/cm3
Driver and passenger            24 psi          33 psi          -
				1.7 kg/cm3      2.3 kg/cm3
Driver with occupied sidecar    24 psi          27 psi          27 psi
				1.7 kg/cm3      1.9 kg/cm3*     1.9 kg/cm3
Driver and passenger            24 psi          38 psi          27 psi
plus occupied sidecar           1.7 kg/cm3      2.7 kg/cm3*     1.9 kg/cm3
* with 4.00x18 tire.

Dimensions (without load)

Overall width **                26" (660 mm)
	R69S:                   28.4" (722 mm) engine width
Width of solo handlebar **      26" (660 mm)
Width of sidecar handlebar **   29.3" (745mm)
Overall width of motorcycle
with attached sidecar **        64" (1,625 mm)
Overall height                  38.6" (980 mm)
Saddle height                   28.5"   (725 mm)
Overall length                  83.6" (2,125 mm)
Overall length of motorcycle
with attached sidecar           94.4" (2,400 mm)
Wheelbase, solo                 55.7" (1,415 mm)
Wheelbase with sidecar
attached                        57" (1,450 mm)
Track width, motorcycle
with attached sidecar           43.3" (1,100 mm)
Ground clearance                5.3" (135 mm)
** without blinkers

Weights             R50          R50S         R60          R69S          R69
Curb weight *       436 lbs      436 lbs      436 lbs      445 lbs       445 lbs
		   (198 kgs)    (198 kgs)    (198 kgs)    (202 kgs)     (202 kg)
with sidecar        705 lbs      (705 lbs)    705 lbs      (714 lbs)     714 lbs
		  (320 kgs)    (320 kgs)    (320 kgs)    (324 kgs)     (324 kgs)
Permissible total** 794 lbs      794 lbs      794 lbs      794 lbs       794 lbs
		  (360 kgs)    (360 kgs)    (360 kgs)    (360 kgs)     (360 kgs)
with sidecar       1,323 lbs    (1,323 lbs)  1,323 lbs    (1,323 lbs)   1323 lbs
permissible axle loads
Front               331 lbs      331 lbs      331 lbs      331 lbs
		  (150 kgs)    (150 kgs)    (150 kgs)    (150 kgs)
Rear, solo          496 lbs      496 lbs      496 lbs      496 lbs
		  (225 kgs)    (225 kgs)    (225 kgs)    (225 kgs)
Rear, w. sidecar*** 705 lbs      (705 lbs)    705 lbs      (705 lbs)
		  (320 kgs)    (320 kgs)    (320 kgs)    (320 kgs)
sidecar wheel       353 lbs      (353 lbs)    353 lbs      (353 lbs)
		  (160 kgs)    (160 kgs)    (160 kgs)    (160 kgs)

Maximum occupancy (including driver): solo, 2 persons; with sidecar, 3 persons.

* Curbe weight = weight of the motorcycle with fuel, lubricants and tool kit.
** Permissible total weight = curb weight + passengers + baggage.
*** with 4.00x18 tire.

The speeds given below are maximum speeds of already run-in motorcycles.  The
speed is largely dependent on the air resistance caused by the rider's size,
position, clothing etc.

			R50         R50S        R60         R69S
solo, normal            81 mph      90 mph      84 mph      100mph
sitting position        (130 km/h)  (145 km/h)  (135 km/h)  (160 km/h)
Solo, crouched          87 mph      100 mph     90 mph      109 mph
position                (140 km/h)  (160 km/h   (145 km/h)  (175 km/h)
Sidecar attached        62 mph       -          69 mph      -
			(100 km/h)              (110 km/h)

Acceleration            R50         R50S        R60*        R69S
zero to 50 km/h         3.2 sec     3.2 sec     4.5 sec     2.6 sec
(31 mph)
zero to 60 km/h         4.1 sec     4.1 sec     6.0 sec     3.3 sec
(37 mph)
zero to 80 km/h         6.8 sc      6.1 sec     10.3 sec    5.3 sec
(50 mph)
zero to 100 km/h        10.3 sec    9.2 sec     16.5 sec    7.5 sec
(62 mph)
zero to 120 km/h        14.3 sec    12.9 sec    -           11.1 sec
(75 mph)
zero to 140 km/h        -           19.5 sec    -           16.0 sec
(87 mph)
1,000 m (.62 miles)     33.6 sec    31.0 sec    39.9 sec    30.1 sec
with standing start
* with sidecar and 132 lbs (60 kgs) of ballast.

Fuels and lubricants    R50, R60, R69           R50S and R69S
Fuel                    regular                 super
Fuel tank capacity      4.5 US gals. (3.75 Imp gals; 17 liters)
including a reserve of  approx. 1/2 gal (2 liters), for about 20 miles (30 km).
Lubricants              only use high-grade greases and oils recommended by
			your BMW dealer

Engine                  For winter and transition periods:
			Brand name multigrade HD oil for gasoline engines,
			SAE 10 W 30.
			For the summer months:
			Brand name single-grade HD oil for gasoline engines,
			SAE 30.
			For sustained sporty driving and at very high temperatures
			SAE 40.
Caution!  to replace a multigrade oil with a single-grade type or vice versa,
it is absolutely necessary to completely drain the actual oil as these two
types are not always compatible one with another.
			Quantity: .52 US gal ( .44 Imp gal; 2 liters)

Transmission            SAE 10W 30 HD oil for gasoline engines, summer and winter;
			quantity: .21 US gal (.18 Imp gal, .8 liters)
Drive shaft housing     SAE 40 engine oil, summer and winter, 9 cu. in. (150 cc)
Bevel drive             SAE 40 engine oil, summer and winter, 9 cu. in. (150 cc)
Consumption             Fuel consumption depends on the mode of driving and the
			driving speeds (computed according to German Standards,
			DIN 70030):

			R50            R60         R50S    R69S
			solo    sidecar solo    sidecar
miles per US gal        46      46      47      36      45      44
miles per Imp gal       55      48      56      43      54      53
at a speed of (mph)     61      47      63      51      68      69
Oil consumption         approx. 1 to 1 1/2 quarts per 1,000 miles

Frame and engine numbers ('should' be the same).

R26     340001-370236
R27     372001-387566
R50     550001-563515
R50/2   630001-649037
R50S    564005-565639
R60     618001-621530
R60/2   622001-629999  1810001-1819307
R69     652001-654955
R69S    655004-666320


- What can I expect when I buy a /2 BMW? What do things like top end rebuilds

You can expect a lot of trouble, unless you buy a fully restored bike with
bills, a journal and detailed photo's of the restauration. These bikes were
very cheap in the seventies. A lot of guys used them intensily, without too
much maintanance. The bikes were transformed to dirtbikes and choppers. And
they who didn't use the hacksaw to improve their BMW, usually tried to cut the
running costs, by installing parts from later models, which fit in a lot of
cases. Aftermarket silencers, tail and front lamps, seats etc. are also common.
Really cared for bikes, which you can run as "authentic and original" are
rare. And it is difficult to find the right looking second hand parts to
restore a hacksawed bike to this type of used but nice finish.

It is not so difficult to restore to a glossy, as new, type of bike. Virtually
all parts are still available or being remanufactured. At the veteran scene
in Europe, the /2 is a very common sight. So there is a large industry around
them. But be aware, not all remanufactured parts are of the same quality as
the originals, and quite a few parts are manufactured in batches. When you
miss the batch, you must wait until the next one starts. At the moment (10-'94)
wheelrims are unobtainable, because Akront in Spain had fire damage this summer.
This is just an example, but characteristic for the situation. Nonetheless,
the parts supply is very healthy

A lot of people are afraid for the mechanical state of their purchase. But
the costs to repair the mechanical damage are usually less than the visual
aspects. New or good second hand fenders, lamps and tanks are very costly.
Paint spraying is expensive, just as all those little bits and pieces, like
rubbers, emblems, nuts and bolts, etc.

Here are some areas to watch out for:
- Get a workshop manual. Clymer or Haynes. The original BMW workshop
  manual is not very detailed. A good German book is:
  "1000 tricks fuer schnelle BMW's" by H.J. Mai. ISBN: 3-613-01117-4
  Also very usefull is a parts list. It contains exploded diagrams of
  all the parts of your bike. Very usefull for reassembly-time.
- All the bearings in the cycle department. Especially headstock bearings
  are mostly scrap. You can update to tappered bearings. My bike also had
  very bad swingarm and wheel bearings.
- Watch out for signs of accidents in the past. Check the wheel allignment.
  Also common in the past was to remove the saddle mounting bracket, when
  another saddle was installed. The bracket should have two groups of
  6 holes, and the saddle uses the 6 rear holes.
- Shockabsorbers from Boge aren't the most reliable items. You can swap
  them for Koni dampers.
- The aluminium wheel rims are mostly heavily scratched and pitted. Polishing
  them is a horrible task. New rims are available.
- Other aluminium items, like the rear swingarm nut and the suspension parts,
  can be polished. Restoring to the 'right' original dull finish is more
- There is not so much chrome, so the chrome bill will stay reasonable. New
  items are available, but usually not of the highest quality.
- Check the fenders for corossion damage. Especially the rear one is prone
  to rust. There is a wiring loom tunnel in there, which acts as a most
  perfect moisture trap. Watch out for bogged repairs with polyester.
  New fenders are horribly expensive.
- The headlamp shell is mostly rather dented and not round anymore. It needs
  a good craftsman to recreate the right shape.
- Tank can be rusty inside, when stored empty. Special sealing kits are
- The petrol tap will be leaking. Unless there is a later type fitted.
  The original tap has a cork lining which isn't for sale, and is difficult
  to make on your own. When you keep the tap always wet with petrol, it is
  possible to keep it reliable.
- Lots of bikes miss the original dim and horn switches. They are being re-
  made, but idotely expensive. The correct type has a sliding dimmer switch
  instead of a toggling switch.
- The battery tray will be affected by rust, but it is made from thick steel.
  More serious is it when acid has attacked the lower frame cross tube. There
  could be an extra "unoriginal" hole.
- All rubers probably will be perished, but are readily available.
- Saddle's are being remade. Also parts are available. But it is very difficult
  to exchange the rubber saddle top whitout machinery. Maybe it is wiser to
  order a complete upperpart.
- Dual seats and the miscelaneous parts are also still available, and are
  available on fleamarkets, as most people nowadays prefere a saddle.
- I hope your speedometer is still functioning. They can be repaired in a
  VDO workshop. When you shop around on the fleamarket for a replacement,
  you must look for a speedo that fits the cardan ratio.
- The engine is a reliable unit. But you will need an overhaul sometime:
- New valves and valve guides. The 8mm valves of the R69 and R69S are very
  strong, but I would advise you to exchange the 7mm valves always.
- Pistons in all sizes are readily available. Only the R69 and the R50S are a
- Small end bushes are not too strong. Big end roller bearings are strong, but
  they depend on clean oil. That can be a problem, because the thrower plates
  on the crankshaft, that clean the oil by centrifugal force, are full with
  sludge after +/- 50k miles. To clean them, you have to dissasemble the whole
  engine, so it can be neglected in the past.
- I haven't dismantled a gearbox yet, but it is a relaible unit. Even when
  maltreated it can stand up for a long time. When you have to adjust the
  gear selection mechanism, you must bend the forks until correct. This is
  an akward business.
- The clutch is prone to the normal tear and wear. When you exchange the
  clutchplates, check the height of the diafragma spring. Look also to the
  splines in the cluth plate and on the gearbox input shaft. They need their
  spline lubrication job now and then.
- The electrical department is not very complex. You need a new wiring loom
  when the wires are brittle. Not too expensive.
- Check the dynamo stator. Its rings should be clean and sparkling. When not
  you can turn them down, and cut back the isolation.
- Check if the magneto has a healthy spark. If not, maybe the rotating magnet
  isn't positioned correctly. Look it up in the workshop manual how it should
  be done and set it very precisely. When this doesn't help most probably the
  windings are shunting. The magneto has a hard life in a hot environment, and
  the old shellack insulation can be weakened after such a long time. When
  the bike has problems with restarting when hot, it could be a bad condenser,
  but more probably it is such a bad magneto winding.
- Putting the rear fender back in place is quite a job.


Were can I find parts?

All BMW dealers should be able to supply you with at least the consumables.
But it is better to check out the specialists. Here are some on both sides
of the Atlantic.

Adress list of German spare part suppliers. Specially pre 1970 stuff.
These shops have a mail order service.

Uli's Motorradladen
Ulrich Seiwert
Gutleutstrasse 144
60327 Frankfurt
tel: 069/239319
fax: 069/233840

Theofried Jeckel
Schutzenhausstrasse 11a
65510 Idstein
tel: 06126/70864

S. Meyer
Bahnhofstrasse 22
67586 Hillesheim/Rheinhessen
tel: 06733/8195 or 7281
fax: 06733/8134
Only R24 - R27 stuff

Martin Kornhas
Nordliche Uferstrasse 14
76189 Karlsruhe-Rheinhafen
tel: 0721/592025
fax: 0721/592026

Rudi Vorholt
(no adress known)
66839 Schmelz/Saarland
tel: 06887/6954
fax: 06887/1254

Motorrad Stemler
Garschager Heide 39
5630 Remscheid 11
tel: 02191/53067
fax: 02192/590349

E. Breindl Grope
Querumer Strasse 26a
38104 Braunschweig
tel: 0531/375737
fax: 0531/377763

for books, manuals and parts lists:
WK Verlag
Lagesche Strasse 105
D-32108 Bad Salzsuflen
tel: 05222 - 92750
fax: 05222 - 927550

This list is not tested, not complete, nor for ever up to date.
But it is sampled from the German motorpress, and therefore rather
reliable. Most of these supliers have a spare part and price list,
to be obtained by sending +/- DM 10,- to them. When you get a spare
parts list, it is astonishing what is available. You can assemble
a complete /2, when you have the money.
The Huge spare part heap of Pfaffen Ag. is recently ('93) sold to
Motorrad Stemler and Rudi Vorhold.

A good mail order service is available in the Netherlands. I do most
of my business with them.
De Hobbyist
Kraakstraat 5
6013 RR Hunsel
tel: 04756 - 6888
fax: 04756 - 6900

Wheelbuilding, rims and spokes, cheap and good:
De Haan Wheels
Ambachtstraat 25
5481 SM Schijndel
tel: 04104 - 76196

And a very good workshop for crankshaft rebuilds and all other engine

Dotterbloemstraat 30
tel: 010 - 4185090

Some specialists in the US. List is from Phil Rose:

BLUE MOON CYCLE              (404) 447-6945
20 Skin Alley
Norcross, GA 30071

BOBS BMW                     (301) 924-5155
10630-Y Riggs Hill Rd.  FAX  (301) 776-2338
Jessup, MD 20794

Elkridge, MD                                      (410) 379-0106

BMW MOTORADD of St.Louis     (800) 999-1269
4011 Forest Park        FAX  (314) 531-8837
St. Louis, MO 63108

BING AGENCY INT.             (800) 448-4819    "MOVING SOON"
824 South Broad         FAX  (402) 721-0263
Freemont, NE 68025

BLEY USA INC.                (708) 437-0671  Crankshaft Rebuilds
No address yet               Expensive but excellent !

Some accessory sources:

Bob' used Parts
Maryland, US
Replica Enduro tear drop bags.
tel: 301 9245155

Theofried Jeckel
Heinrich products, Meier tanks.
Frankfurt, Germany
tel: 06126 70864

Ian MacKintosh
Replica Peel fairing
California, US
tel: 714 4964964

Craven Equipment
Original sixties rigid saddle bags
Cinderford, UK
tel: 01594 825010

When I want to overhaul the engine, gearbox etc, do I need a lot of
special tools?

It all depends on your workshop. It will be very helpfull if you have
a lath. You can make the nicest tools with a lath and a standing drill.
But you can also improvise lots of tools with rough lumps of steel and
welding equipment. Most gears and bearings have a tight pressfit, so you
need very sturdy tools.

You should buy an exhaustnut wrench. There are two types, for the
finned exhaust nuts of the R69, R50S and R69S. And the nut to
remove the flat nuts, with little holes in the side on the R50 and
R60. Both are not extremely expensive, but invaluable.

Another thing is a heating device. A blowtorch is too hot. It will
melt the aluminium castings. I always use a large electrical
cooking plate.

Some tools for engine (dis)assembly:
All sizes in milimeter

- To release the clutch spring pressure, you need two or better
  three M8x1 fine threaded screws with nuts and some 40mm long.
  The cardan housing is fastened to the rearwheel casting with
  studs that have M8x1 and normal M8 thread. When you use these,
  you can srew the fine thread in the clutch and use the course
  thread to release the spring.

- Clutch center tool:
		       (  30  )(4.5)
	   -----------+________                      ^
			       +                ^        
			       + ---\  8mm
			       + ---/          20.4  23
	   ___________+--------+                v

- To pull the dynamo and the magnet from the crankshaft and the
  camshaft, use a strong steel stift of 60x6mm. This should be
  strong, because, when it bends, you have a big problem. Put the
  stift in the appropriate opening and push with an M8 bolt.

- Universal puller plate
  200x80x8  with one hole the middle of 8.5 mm
  and two slots of 8.5x45 on both sides of the hole
  with 15mm in between:

       ---------    *    ---------

  To be used together with M6 and M8 studs to pull of the large
  timing gear housing on front of the engine. And together with a
  steel bush of 48 outer diameter and 35.5 inner and some 100 long
  (you should take some messurements to see how precise this is,
  but you should get both ends true parallel),  and a M8 stud to
  press the front crankshaft bearing and the crankshaft gearwheel.

- The flywheel puller

	     +  |  |      | M16|      |  |  +
	     +  |  |    --|    |--    |  |  +
	     +  |  |   |          |   |  |  +
		hole    (  28mm  )    hole 11 mm

		 |(       66mm        )|
	     |(            88mm            )|

  You need an M16 bolt to press and two M10x1 fine threaded bolts
  to attach the puller to the flywheel, which accomodates two threaded
  holes for this purpose. Also you must put a strong steel disk of
  27 mm outer diameter between the M16 bolt and the crankshaft to
  protect the threads overhere. The front suspension units are fastened
  with M10x1 x48 bolts.
  A simplified version could consist of a piece of U profile, with
  a 18mm hole, and a M16 nut welded over this hole. When this nut is
  fixed, measure the place of the 11mm holes and drill them.

- The R69 and the R69S have a special rear crankshaft bearing. This
  bearing can cope with the flexing of the crankshaft, but during
  assembly it needs to be fixed in place. You really need a lath
  for this tool. Dimensions:
				   |(  31      )
				   |(  24   )
				   |(  18 )        The dimple is 1.5 deep
	     ^      +              |       |      +     ^
	    30      +---+          |       |  +---+     24
		 ^19    +          |   +---|  +         v
	     v   v      +----------|...+------+
				    ( 19  )
		    (           71.5             )
			(         50          )

  To be fitted with the large flywheel bolt.

- To fit the crankshaft in the rear bearing house you should use enough
  heat to let it slide in. But sometimes you have to use some extra force.
  Don't smash with a hammer on the front of the crankshaft, but you can
  use this trick: get an old flywheelnut (M18x1.5) and drill a hole in the
  middle with M8 thread. Together with a stud and the universal plate
  and some lumber, you can pull the crankshaft in to place.

- You can remove the camshaft with the universal plate, two 70mm wooden
  bars and a M8 thread. Put the lumbers under the plate and pull the
  complete camshaft together with gearwheel and all the front bearings out.
  (The R69 is the only one with two frontbearings). The rear bearing can
  be pulled out with some hooks, and a rope, when the whole engine casting
  is being heated, to remove the crankshaft.
  For (dis)assembly of the camshaft wheels and bearings, you can also use
  the universal plate.

- Pulling the crankshaft gearwheel is done with a normal two arm puller.
  Maybe you must ground it down on some places to make it fit. Use a clamp
  to press the two arms together. Protect the crankshaft with a bolt. And
  don't forget to remove the seegerring on the pre '63 engines...

- Mandril to remove the wheel bearings from the brake side:

		 (  20  )
		 |      |       ^  15
		 |      |       v
		-+      +-
		|        |
		|(  25  )|
		v        v

- Key to remove the special big wheel nuts.

	 |      (       44        )
	 |      o        O        o
	 |                          steel plate 8mm thick

  Make one 10 mm hole in the middle and place two 5 mm pins on 44 mm.
  Drill out the holes in your wheel nut until 5 mm. For the pins, I
  used M6 bolts, turned down to 5 mm. With the remaining thread, you
  can attach them to the steel plate.
  The joke is, to put the steel plate with the pins on your wheel. Put
  an M10 stud though the 10mm hole and the wheel, and fix everything with
  some nuts and rings together. Now you can put a lot of force on this
  tool, without the risk of damaged keyholes.

- A setup to disassemble the front suspension units is easy to make.
  The goal is to reach the shock absorber arm with a 9 mm spanner.
  Make from plywood two plates one with a dimple to hold the underside
  of the unit in place, the other with a 58 mm hole to go over the 
  upper aluminium part and on to the black cover. Now make some extra
  holes in the plywood for two long M6 studs alongside the suspension
  unit. You can press the unit together now, but most probably the
  upper aluminium part will be oxidized together with the black cover.
  So you must put a steel rod through the upper alu part, and attach
  it to the studs with some nuts, steel plates and wire. Now you can
  screw down the plywood with two nuts on the studs.

I want a sidecarhack, and someone told me to get a /2 frame and
put a new BMW boxer engine in it. What is involved in this?

The /2 series bikes were factory aproved sidecar machines, as
opposed to all the post '69 BMW's. The frame is very sturdy and
has standard attachement points for a sidecar. You only need
a special front engine bolt and two upper bolts, together with
the sidecar and it's attatchement hardware. The necesary holes
are already available. The Earless front fork is also a plus,
because ity is very strong, and because you can change the steering
dynamics for sidecar usage.

In the fifties and sixties, you could buy a complete outfit,
consisting of a R60(/2) with a Spezial sidecar. The latter
actually was a Steib TR500 with BMW logo's. Or you could buy
the R26/R27 with a Standard, being a Steib LS200 with BMW logo's.
Other popular sidecar's were the Steib S350, S250, S500 and S501,
The Danish Bender and the Dutch Hollandia.

Nowadays you see a lot of /2's with an Ural or Dnepr sidecar. This
is a copy of the military Steib sidecar. Sometimes you also see
the Tsjechian Velorex or the ex Eastern Germany Elastic. (IMHO not
so attractive)

/2's with an old Steib or a Dnepr sidecar are a beautifull sight,
but are not very powerfull. The R60/2 with sidecar has a topspeed
of 110 km/h. In modern trafic a bit low maybe. And because it is
relatively easy to exchange the engine for a post '69 boxer engine,
this is common practice. So you can put a R75/x or a R90/6 engine
in there and get a lot more power. But be aware, don't overdo this
because a real high speed sidecar outfit needs a lot more modifi-
cations, like stronger brakes and lower wheels for better stability.

David Makin sended me this article about what you can expect
when swapping engines:

This article summarizes experience in building two old frame/new
motor "conversions".  One is an R50/2, rebuilt with an R75/7
powerplant and fitted with a large Bender sidecar.  The other is a
1966 R69S, fitted with the engine from an R90/6 but a four-speed
gearbox from a /5.
Basically we transplanted the modern engines complete with carbs
and exhaust, gearbox, drive shaft, cables, hand controls, and
instruments into the /2 chassis.  Building the conversions was aided
by the availability of an empty /7 crankcase, and a spare gearbox.
Thus, I was able to offer up a lightweight drive train to the /2 frame
without a lot of effort to test assemble.  Here's the modifications
required to the /2 frame to fit a /5/6/7 engine/gearbox:
-- trim the sidestand bracket so that it presents a smooth face on
the inside
--shorten rear tank mount about 3/4"
--reweld the triangular frame gusset at the V of the top rear frame
tubes under the seat  about 3/8 of an inch higher up the tubes, so
that the air box can be fitted. [There is evidently some considerable
variation in /2 frames; we've since learned that other conversions
have required spreading the frame to accept the motor, and dimpling
the frame to clear the oil filter plate.]
With these modifications the  engine can be installed less timing
coverand starter cover which have to be fitted after the main lump
is in.  With the engine in place, the gearbox can be installed in the
normal way.
At this point two more major tasks remain:  the Earles fork, which
may hit the timing cover, and the fact that the drive shaft was shy
of the output flange by about 1/4  inch.  To deal with the easy part
first, we took the /2 drive shafts out of the /2 swing arm, and
replaced it with /6 /7 shafts.  The later drive shaft is about 5 or 6
mm longer, but the /6/7 "bell" has to be turned down to match the /2.
You cannot use a /5 drive shaft and bell; there isn't enough metal in
the bell to allow sufficient machining.
At the front, the lower brace between the legs of the Earles fork hit
the timing cover.  Interference  apparently depends on what fork you
are using; the R69S fork, for example, had a flatter tube in this spot
to clear the harmonic damper.  With a non-ventilated /5 timing
cover, the fork just cleared -- but not with enough room for safety.
The '63 R50 with a /7 engine had about 3/16 of negative clearance.
This was  reduced  to 1/16 simply by filing the ribs off the front of
the /7 timing cover.   To make things fit, an eliptical slice of tube
was hacksawed from the fork brace.    The opened-up tube was filed
to a smooth curve, and test-fitted to the frame with the timing
cover in place.  Once the desired curve was attained, 1/8" mild steel
was MIG welded over the hole, shaping it very carefully to exactly
match the tube.
At this point, the engine/gearbox is in place, the drive shaft
installed, and the front fork back on.  Take the opportunity to put
tapered roller bearings in the steering head; this is a bit awkward,
as the outer race is a tight fit, but it is worthwhile (I had no problems
with this. Kees).  Now, you face all the really fiddly bits which take
almost as long as the big job of engine, gearbox,  drive shaft and fork.
	After much experimenting,  two Dyna 6-volt twin-lead coils
required for the 750's twin-plug heads were fitted under the tank
between the top tubes.  The voltage regulator and the starter relay
also fit under the tank; careful routing of the original /7 wiring
harness allowed all stock connectors to be used.    There is adeqate
room for a single two-lead coil, but not for the stock large twin 6v
	To fit the large /7 headlight, the /2 headlight mounts were
removed, and the mounting holes enlarged by the simple expedient of
removing the rubber grommets.  New rubber pads were made to go
between the mounting ears and the fork, and by leaving the rubber
grommets out enough width was gained for the complete /7
headlight.  However, the left hand mounting ear had to be modified so
that the very large /7 ignition key/mounting bolt could be installed.
The /7 instrument panel mounts nicely to the /2 top fork yoke, since 
the spacing between the handlebar mounts is the same.  The rear 
portion of the instrument mount was simply trimmed off, and the 
instruments mounted without any rubber bushings.   Much more 
simply, a  /5 headlight including the instruments goes right in, or 
the /2 headlight, with a change in bulbs and some rewiring, could be 
used.  Both would be more "period" and might be preferred by some.
At the rear the /2 wiring harness  can be used for the tail light, 
splicing the wiring to the /7 main harness plug for stop, tail, turn
and ground.
Finding a suitable battery and developing a battery tray takes some 
time.  Originally a battery tray was made to bolt to the original tray 
mounts at the rear and to the bottom of the seat bracket at the
front, offset to the left away from the drive shaft housing.  There
was then just enough room to install a YBL-14A 12 volt battery.
Later, a Mk II version was made, somewhat simpler, that holds the 
battery in a central position.and is much tidier although the
clearances are very  tight.  The small battery has presented no
problems so far; next time we'll seek out a taller ATV battery which
we're told is a better fit and holds more acid.
The /5/6/7 exhaust pipes with extensions mate up to a pair of R69S
stainless mufflers.  A complete purpose-made stainless exhaust
pipe and muffler set is available for these conversions from EPCO,
which would be better still.    EPCO also makes a long-inlet muffler
which allows use of the cheaper stock pipes shortened to suit.
How does it all work?  Very well, but the brakes, remember, aren't
up to current standards.  However, the styling and sidecar capability
of these frames is very attractive, particularly with the modern
powerplant and 12 volt electrics.
Several MOA articles provided valuable research including
August 1982, September 1982, November 1982, March 1983,  and
July 1991.

How should I attach a sidecar to my /2 BMW?

This is an abstract from the official BMW workshop manual. Do anything
you think is practical. For example, it's not very necessary to use
the sidecar gearbox.

The subsequent modification of a solo motorcycle to accomodate a sidecar
involves a number of technical changes wich in every case should be
reserved for a special BMW garage.

1 Replace the bevel gear setin the rear axle drive. 4.33:1 for the R50
  and 3.86:1 for the R60.
2 Exchange the transmision against another with sidecar ratio. (R50 and R60).
3 Install modified speedometer with ratio for sidecar operation.
4 Equip front and rear suspension with thicker springs.
  Set the swinging arm bearing on the front fork in the forward location
  on the fork.
  And the front wheel upper suspension mounting into the lower position of
  the fork.
5 Exchange brakelever without stop screw to one with a screwscrew. Srew in
  the stopscrew until a noticable braking effect is obtained, the back of
  until wheel just runs freely, and tighten the lock nut.
6 It is available to exchange the 25.6" solo handlebar against a 28" sidecar
  handlebar. In this case also use the longer control cables.
7 Exchange the wheels with lightmetal rims against wheels with steel rims.
  2.15Bx18 front with 3.50-18 tire and 2.75Cx18 rear with 4.00-18 tire.
8 Replace the front engine mounting bolt by the ball pin to be suplied by
  BMW. For this it is necessary to remove the bushing in the right hand
  frame eye. The new bolt is supplied with a castellated nut, which must 
  be secured with a cotter pin after tightening.
  Install the two eyebolts into the provided eyes on the right side front
  and rear. Remove the paint from contact surfaces for the eyebolts and 
  tighten the nuts with 54 ft/lbs.
9 Remove the blinker light from right handlebar end. Disconnect lead from
  terminal K2(R) of the blinker unit and on its place connect the new lead
  for the blinker light on the sidecar fender. Seal opening in the 
  handlebar with a suitable plug.

// Everything about the hydraulic sidecar brakes deleted //

When attaching the sidecar to the motorcycle, start with the under attach-
ment points. Rock the motorcycle repeatedly sidewise to insure a perfect
seat of the ball joints. Then attach the upper parts and take care to avoid 
any tension in the attachment points.

Recommended sidecar dimensions:
Toe-in  1.2" to 1.6"
Camber  3/8" to 7/16" with motorcycle and sidecar occupied.

The sidecar brake should take hold after the rear wheel brake has already
begun to grip. In general, the total braking action of the front and rear 
wheel brakes of the motorcycle should be so proportioned to that of the
sidecar that the vehicle always tracks well, irrespective of the load, when
the brakes are applied.

The electric jack for connetion of the sidecar lighting is situated under
the seat on the cross brace of the frame. The jack is energized as the 
light on the headlamp is switched on.

What is this magneto? How should it work, and why doesn't it work in
my bike?

This article is submitted by Craig A. Vechorik.

Does your mag igniton BMW start on the first kick?  If properly set up, it
should!  Although many of the old timers are aware how to set up a Magneto,
there are some commonly overlooked items and procedures to remember.  
First of all, disconnect the plug wire from the coil, and using an Ohm meter,
check the resistance of the wire and the plug cap.  It should be ZERO resistance
Before all of the hair splitters out there jump my case, let me make my
standard Disclaimer of the '90s and say that THIS WORKS FOR ME, and has for 
years.   Yea, I know that BMW started using resistor plug caps in '67 in 
response to regualtions governing RF interference.  I still don't recommend
that you use them.  A lot of aftermarket companys will sell you /5 or /6
plug caps, but they have a 1000 ohm resistor built in them.  If you can't find
a source of non resistor caps, head for a chain saw dealer.  
  Remember, that the faster a Mag spins, the hotter the spark.  At the speed
that you can kick the engine over, the spark is relatively weak, and using
resistor caps and plugs is to invite hard starting.  
  Another problem in starting can be the condensor.  ALWAYS carry a spare one
with you when you ride a /2, because if it ever fails (and they do) it will
quit on you, and will not restart.   You don't have to buy one from BMW, either.
The condensors I use are for a V-8 Ford, '73 351 ci, and they have their own
bracket already on the condensor, and the wire lead has a spade lug on it.
This consensor will produce a strong blue spark, and last for many years.
    The initial setup of the Magneto is important if it is to produce a strong
spark.  Check to see if the scribed line on the rotating magnet lines up
EXACTLY with the bottom of the "V" notch on the brass plate that the points 
mount on, when the "S" mark of the flywheel is lined up with the stationary
mark on the crankcase.   If it is off slightly, loosen the two 6mm nuts
that secure the body of the mag to the timing gear cover, and rotate the body to 
the left or right until a perfect alignment is obtained.  I have seen folks   
use a timing light to check the timing while the engine is running, and to
obtain the correct timing, they will move the body of the Magneto.  this is 
NOT the way to set the timing.   If you remove the centrifugal advance, you
will notice that the points are mounted on a seperate breaker plate, which
is held down by two screws.   That is the plate which needs to be moved when
setting the timing.
    Another thing which will cause coil failure, (which is common) is the
ventilation system for the electrics.   Ever wonder what that little breather
air cleaner thing is doing under the 1/2 moon cover on top of the engine?
Air is drawn in through the notches on the front engine cover, over the
generator and coil, through the little breather, into the Carbs. 
Check that little breather, clean it, lightly oil it, and put it back.
    Keep in mind that the timing of an air cooled engine is critical to the
operating temperature of the engine,   One can easily time a /2 engine
staticly.   By aligning the "S" mark on the flywheel to the stationary mark
on the window of the crankcase, and then using a test light or an ohm meter
on the points.  (the wires from the coil and condensor must be disconnected)
If you use a test light, you must use a battery also, to light the test light.
You use the test light AFTER you have set the points to their proper gap.
You rotate the breaker plate clock wise (but all I've ever seen is a digital
watch P^) )to advance the timing or counter clock wise to retard the timing.
The idea is that you want to postion the breaker plate so as you rotate the
engine, as the "S" mark S-l-o-w-l-y passes the stationary mark, the points
open, turning off the test light, or showing an open circut on the ohm meter.
     In the end, except for the initial set up and starting of the engine,
it doesn't matter too much where the "S" mark appears in relation to the 
stationary mark, when the engine is running at idle.  What does matter is
where the "F" mark or full advance mark is with the engine running at riding
speeds.  The only way to check this is with a timing (strobe) light.
This brings us to another common problem.  When you use the timing light,
do you see two images in the window? At idle or at Full advance? 
If you do, shut the engine down, and rotate the engine until the points are
at their widest.  Check the gap with a feeler gauge, and figure out which
blade of the gauge fits the gap the best.  Then rotate the engine 360 degrees,
and check it again. In the ideal situation, with a good advance, assuming that
the shaft of the rotating magnet, that the advance mounts on, is not
bent, or that you had inadvertently had a speck of dirt on the taper between
the camshaft and the rotating magnet when you mounted it on the cam, the
point gap should be the same.  You do know that both cylinders fire at the
same time, but only one of them is on the compression stroke, while the other
fires during the exhaust stroke.  When you see two images in the window, 
one side of the advance is worn more than the other, and the points are opening
to a different gap from one side to the other of the advance. 
Slash 5 & 6's will do this also.  If they still have points in them.  You can
cure a /5 or /6 with an electronic inductive ignition system.  Too bad that 
there is not an inductive system for a mag.  The wider the images appear in the
window, the more worn out the advance is.  You can see this condition in the 
header pipes of the engine.  If one is "bluer" and the blue extends further 
back on the pipe, one cylinder is timed slightly different, and is doing most 
of the work. On a machine in this conditon, it is hard to get it to run right,
it seems as if the carbs are slightly out of sync, and you get vibration at
all speeds.  Messing with the sync of the carbs won't help it either. 
the only thing you can do is buy a new advance.