Miscellaneous Tech Questions

Table of Contents:

/2 Toolbox Hingepins - fabricating hingepins for /2 Toolbox Carburetor Repair - stripped idle mixture screw repair
R26 Ignition CutOut - Fixing ignition cut out Removing Swingarm Bearing Races
R50/2 General Questions R26 Engine Removal
/2 Timing Questions More Timing Questions
/2 Timing Gears Timing an R27 Camshaft
R27 Output Shaft Steering Head Shake
Steering Head Bearing Race Removal Replacing Earles Fork Swingarm Bearings
Idle Speed Problem Disassembling Earles Front Shocks
Diagnosing Potential Charging Problems Loose Kickstart Lever
Magneto Coil vs Coil and Breaker Ignition Removing the Steering Stem Lock
Repairing bar end turn signals Cheap signal copies from the authentic Hella
Patch holes in petcock bodies Technical and How To Articles

/2 Toolbox Hingepins

Roger Albert writes:

Well, I'm slowly pieceing the /2 back together (slower than I ever thought I was capable of) and have hit a small snag, insofar as 1 of the toolbox hingepins and the single fender pin are lost at the painters.

If your a cheap kind of guy, you can fabricate these out of a soft finish nail. Cut a slot in one end, after you cut it to length, so you can spread it slightly, to keep it retained in the hinge. If you want to do it right, you can buy these:
16 11 4 080 176--$8.00--top tool box hinge pin R24 R26 R27 R51/3 & /2 6.5-gallon tank ss
16 11 4 080 178--$7.00--side tool box hinge pin R25/3-R50-R69S ss

The pin diameter is 6mm. You can get a long 6mm socket head cap screw, and saw off the head, and that will work fine as a pin if you cannot find any thing else that diameter.


Carburetor Repair

Chris Micca writes:

The idle mixture screw on the right side carb on my R69S is stripped.
 Is this repairable?

There is a way. Locktite makes a Thread Repair Kit. It consists of an epoxy-like stuff and a release agent. You have the hole perfectly clean with carb cleaner, mix the goo up, apply the release agent to the threads of the mix needle, pile the goo on the threads of the mix needle, and stick it in the stripped hole on the carb, and wait. The stuff is pretty strong, but you will have to be careful not to tighten the lock nut very much, or you'll pull the threads you made out. I have fixed pot metal carbs and the left hand threaded holes of mirror mounts of /5's this way, with good results.The alternative is to send the carb to Bing USA and they can install a thread insert in the hole.

Can I use a left side carb body on the right side?

No... You won't be able to put the air tube on if you do.



R26 Ignition Cutout

I seem to have some sort of alternator problem. When riding at freeway speed for any length of time, the alternator light tends to glow at anything over 70mph.

You mean generator... but, anyway...

Running an R26 that fast will cause the brushes to float, if the brushes are getting short, or if the tension springs are weak, or if the commutator of the generator is out of round. Check to see if the surface of the copper commutator is running true.

The engine also started to cut out but I think that may have been a fuel problem. Any clues?

Ah HA! Yeah, the vibration is breaking the contact in the ignition switch in the headlight. I've had my R26 do that at high speed.

Bend the stationary contact arm (that has the dog leg bend in it) just a little closer to the switch plate. If you look at the contacts (the one on the dog leg arm, and the contact that moves on the upper arm) when you shove the key in, I'll bet you will see that they are burned from arcing due to poor contact pressure.


Removing Swingarm Bearing Races

Ron Rohner of Quakertown, PA writes:

I took my R69S completely apart these past couple of days... can you tell me how to get the bearing races out of the rear swingarm and the front swingarm? The steering head races came out easy... you can knock them out. But these... I have no clue. Do you use heat or cold?

The easy way to do this is to take the swing arms to a good heliarc welder, and have them weld a continous bead, all the way around the surface of each race, where the rollers used to run. Needless to say, do this BEFORE you paint. When it cools off, the 30203 bearing race will just fall out, it you rap the swingarm on the surface of a wooden bench. It is just that easy.

Save one of the old races, that he has welded on, and use it as a driver to put the new races in with. Since it is now shrunken from the welding, it is undersize and will not get stuck in the hole if you use it to drive the new races in.



R50/2 General Questions

Sam Barnes writes:

I completed the breakdown of the R50/2 engine reaching the rear oil slinger. Like the front slinger, it also was full of crud.

I trust that you did not find any radial play in either rod. Axial play is OK but any radial play is not.

My R50/2 engine produced a steady whiff of smoke (could be black or blue) when it idled. The plugs were dark brown to black. The engine compression reading was 90 to 100 with the engine warm and the throttle wide open. I rebuilt both carbs with new Bing kits using stock jetting. The valves appear in good shape. The cylinders are smooth without noticeable scoring.

I want to know how to determine if the cylinders require boring (hopefully not) or will oversize rings do? Should I just replace the rings with stock rings? The odometer reads 30,000 miles.

I would think that all you will need is new rings. If the engine was overheated sometime in the past, the heat can ruin the tension of the rings, and will cause oil usage.

The allowable wear is as follows:
Original operating clearance, piston to cyl wall = .0025
Max. allowable wear = .005
Total max. clearace = .0075

Measure everything, and see what you have.

I enjoyed Roland Slabon's book on restoring BMW motorcycles. On page 92 it indicates that rotating valves were installed in R50/2 engines in October 1966 beginning with engine number 641473. The engine number on my R50/2 is 641915. Could you please elaborate on rotating valves?

The rotating valves are just that. They slowly rotate during operation, thereby improving the life amd efficiency of the valve by a constant lapping motion during operation.

Also, there is a reference to valve clearance problems on /2s prior to 1967. This is the result of a faulty aluminum alloy mixture. Should I be concerned about this? Again, any information is greatly appreciated.

If you allow the engine to overheat, it can cause the support towers for the rocker arms to recede into the head. This will cause the cylinder to lose the correct head torque, and since the rocker arm moves in toward the block, the valve clearance will disappear. It can become a serious problem.


R26 Engine Removal

Bob Wall of Singapore writes:

I am having problems removing the engine from the frame of my R 26. Obviously you have to remove the coupling BUT what do you have to take off to separate this coupling - the bevel gear housing or the support holding the propshaft cover tube?

Let me help you... The way I do it is to remove the rear wheel, the rear fender, and then the rear swingarm.

Then the gearbox, and then the engine, after I have removed the upper end from the engine.

/2 Timing Questions

Hans Kaufmann writes:

I am writing for some advice regarding my 1967 R50/2. Your assistance has been appreciated in the past. After the restoration of this bike I have never really been satisfied with the performance, and then I tripped over your tech article regarding the two images of the timing mark when using a stroboscopic timing light. Your article seemed to say that if you see two images in the timing hole, then you need to replace your centrifugal advance.

This, however, lead me to consider several possibilities that might account for the lobe on the advance not running concentric. For example: bent cam, bent magneto rotor, bad conical fit from cam to magneto rotor, poor fit from magneto rotor to centrifugal advance, worn centrifugal advance.

I did some measuring with a dial indicator and was hoping for your advice.

Well, yes, it is true that if the shaft of the rotating magnet is bent or wobbling it would show this problem (and I believe that I raised that possibility, by saying that the magnet may not be seated straight on the cam).

First I wanted to see if the magneto rotor was running true. I got an indicated runout of .004-.005" which I was able to correct to .0015" (brass drift & hammer technique).

With the advance connected and torqued, the difference in lobe runout was .0035". The whole advance unit seems to be sloppy but with only 28K miles on the bike and not having another advance unit to compare it to, maybe they're all sloppy. Since I'm the third owner it could be that the advance unit is not from this bike.

That is excessive runout. You need to figure out why. Without the advance mounted, the shaft is showing .0015? That probably is close enough not to dramaticly effect the timing.

However, how did the magneto rotor develop the wobble in the first place? You should remove it from the nose of the cam, and clean both the female tapered hole and the male tapered cam nose, and remount it. And check for runout again. However, your trueing method does work, but you may have compensated for a mis-seated magnto rotor from the presence of dirt or other foreign particles lodged between the cam and the rotor.

Anyway, do you think that the readings I observed would warrant replacement of the advance unit? What does a new unit cost? Is the .0015" runout on the magneto rotor acceptable (I can't imagine getting it any closer with a tapered fit on the camshaft)? What does the fit between the magneto rotor and the advance unit need to be? I can't imagine that one lobe is more worn than the other.

Well, you had best believe that the advance wears that way. I have seem many, many advances where one lobe wears out more and faster than the other, which is the source of differential timing in about 95% of the cases.

The left exhaust pipe is much more discolored than the right and the discoloring goes much further down the pipe as well.

Yes, this confirms that your bike has differential timing between the cylinders. Buy a new advance, and you will be amazed at how much better it will run.

Thanks for the advice. I have just bought a Pentacomm points conversion kit and I am experiencing what I think is spark knock (pinging). I've adjusted the timing so that 9 degrees before TDC is aligned at idle and then with a timing light advanced a little bit to see the "F" mark in the timing window when revved.

The line by the "S" mark should show in the window at idle, around 400 - 600 RPM. For all practical purposes, you need to have the line next to the "F" mark line up in the window when the machine is at normal operational running speeds.

If you have that condition, and you are still experiencing a spark knock, and you are using high test gasoline, the probable cause is that the engine was operated for a long time with a worn out advance unit, and had differential timing. This caused a lot of carbon build up on the crown of the piston and head. The glowing hot carbon can cause this problem, known as pre-ignition. I would pull the heads, and clean off the carbon. Be sure an replace the head gaskets!

Should I advance the timing until the pinging goes away regardless of the timing marks? Maybe I should try adding an octane booster. I'm using Chevron 92.

If you run it long enough, fast enough, far enough, it my slowly clear the deposits, but I would take it apart, and decarbonize the top end.


More Timing Questions

David wrote:

I just picked up a 1960 R60 last weekend. I was told the entire top end needed to be rebuilt. I found that hard to believe after test driving it because in higher gears and higher RPMs the motorcycle seemed to have lots of power. But it appears that the right cylinder isn't getting any spark until higher RPMs. The motorcycle will run on the left cylinder only and then all of a sudden the right kicks in and the motorcycle really takes off.

I took the front engine cover off, started the bike and let it idle. The left head got hot but the right side stayed completely cold, which was the first clue that the motorcycle was only running on one cylinder at low RPMs. Then I noticed, off of the coil on the right side only, a spark going from the end of the spark plug wire to the safety tab below the coil. When I got on the throttle, the right cylinder would fire up and the sparking on the right side of the coil would stop. I was also getting a little bit of backfiring out of the right pipe.

Oh, I also switched the spark plugs and wires from left to right but still the problem stayed on the right side.I took a quick compression test and got 125 lbs. on the left and 95 on the right. The valves seem to make a lot of noise on the left side. The bike also has a brand new Pentacomm in it.

So, any ideas why the right cylinder is kicking in only at higher RPMs and why at lower RPMs there is a spark from the right side of the coil to the safety tab below it? Any help would be much appreciated.

Well, it could be a number of things. This is what you need to check first.

1. The gap between the terminal on the coil and the little metal arm that sticks up from the body of the magneto should have a gap distance of 11 mm. If the bare end of the wire is too long, and sticking way out past the end of the terminal, it in effect closes that distance. The magneto is designed to allow the coil to discharge to ground through those tabs when the plug wire is removed from the plug. If you do not have exactly 11 mm, bend the tab until you do.

2. You probably have resistor plug caps, or perhaps a combination of resistor sparkplugs and plug caps in the engine. For the best performance, do NOT run resistor plug caps. Check your caps and wires for resistance by using a ohm meter. Disconnect the wire from the coil and stick one lead of the ohm meter to the wire and insert the other lead into the plug cap, and take a reading. You should have zero resistance. If you don't, discard the caps, and buy non-resistor caps.

3. Plugs can go bad and have internal breaks in the electrode. This can occur from simply dropping it on the floor. Discard the plug and put a new one in. Bosch w4ac is the number for short reach plug heads.



/2 Timing Gears

Sam Barnes writes:

I am cleaning the oil slingers on my R50. The crankshaft timing gear and camshaft gear bind. The cam gear and crankshaft gear move, but bind at specific areas. The timing marks on the cam gear and crank gear line up properly. These two gears moved freely before disassembly. The cam shaft and gear are true. The crank shaft gear and oil pump gear move freely when the cam gear is removed from the engine. I tapped the posterior of the crankshaft and the gears freed up some. The engine reassembly is correct. The gears move easier with a heated engine.

Do I need to worry about this? Will it resolve on its own when the engine running on its own? The cost of the aluminum cam gear is expensive. The gears meshed smoothly before disassembly they should mesh after reassembly.

Yes, you do need to worry... it will chew up the gears if you leave it as it is. I know what is wrong... the force required to pull the steel crank gear has bent the last millimeter or so of the teeth, where the puller was seated. Happens all the time.

You have two choices. Obviously, the first is to replace the gear. Expensive, and a pain.

The easier and cheaper thing (if you notice, the cam gear is not as wide as the crank gear) is to use a jewelers file on the teeth of the crank gear. Mark the teeth that bind, on the steel gear, with liquid paper. Roll the crank back, out of the bind, and rip a rag into a thin strip. Stuff the thin strip behind the gear, to cover the face of the front main bearing, and with a flat jewelers file, dress the sides at the back of the few teeth that are involved with the bind. Pull the rag out, blow out the filing, roll it again v-e-r-y slowly and check for binding. You must get it to have no binding at all. Repeat this until you eliminate all the binds.



Timing an R27 Camshaft

Carl wrote:

I need an R27 camshaft sprocket, late-style with a timing mark. It does not need to be perfect. I only need it for timing mark set-up. Do you have one?

You don't need a spare one to set the cam to the crank.. This is how I do it. And have been for years on singles.

1. Get a bottle of liquid paper.
2. With the cam out of the block, eyeball down the cam on each lobe, and paint a white line on the face of the gear where the center of each lobe is. That will give you two marks, roughly at
4 o'clock and 8 o'clock on the gear. Then, make a third mark at 12 o'clock in relation to the two marks you made previously.
3. When you install the cam, have the crank at TDC, and set the cam so the
12 o'clock mark is directly in line with the lifter towers and pushrod tubes.

That's all there is to it. Works every time. Promise...



R27 Output Shaft

I have found the end of the transmission output shaft to be damaged. It ends in a bulb over which a castle nut slips. The bulb is fractured- a little piece is broken off, but saved. It seems like this might not affect anything functionally. Or is that shaft ruined?

The shaft is not ruined. That happened when someone attempted to take the drive flange off of the shaft. And they knew not what they were doing. It makes it harder to do, but I have a trick that works. You drill the threads out of a common hex nut, selecting a drill bit the same size as the ball. Before installing the puller on the shaft, you drive the drilled hex nut on the shaft, over the fractured ball, to support it, to prevent further damage.


Steering Head Shake

Lasse Aarønæs of Oslo, Norway wrote:

When browsing through your pages I am surprised to find no comments or advice for solving - for what I have experienced - a fairly frequent problem on the /2 BMWs: the wobbling tendency.

Yes, you're right. I need to put that on the site. It is a common problem that can kill you, if it gets out of hand.

I have experienced this problem on my own 1956 R50, and I have spent time and money to solve it. Well, I can tell you that changing tires....

Correct thing to try. Some brands of tires don't work well on Earles Fork bikes.

...higher air pressure,...

Correct pressure, rather than high, in my opinion, seems to be best.

...new wheel bearings,...

Only effective, if you have the proper preload on the wheel bearings. And you MUST have the proper preload, or it will induce a wobble.

...new front fork bearing,...

Yes, the tapered type is much better than the loose recirculating ball type. I recommend using them. Let me ask you, when you changed the steering head bearings, did you notice how tight the races for the bearings fit the steering neck of the frame? If you had a race that was loose, that is an indication that the bike was involved in a collision in it's past. About all you can do is to use a center punch, and put peck marks around the inside of the seat in the frame, to retain the bearing. That, and use a locking compound on the race. In America, a brand of this retaining compound is Locktite. You want retaining compound that is for stud and bearing mounting. A loose race in the frame, can give you just a little play, which can amplify into an exciting ride!

Also, the preload of the steering head bearings is critical to this problem. Too loose, and the front end will wobble. Too tight, and it will feel as if someone is sitting behind you, slowly leaning left and right, when you are traveling at about 35 mph.

...adjusting rims,...

Loose spokes and/or a badly out of true rim certainly can contrbute to the problem. All of this is a good start. Check the swing arm bearings, front and rear. If they are loose, it can induce the problem.

Some bikes, for some reason, (and I think it may be slight wreck damage in the past) tend to want to develop head shimmy. My '66 R50 was prone to the problem. It had, by the way, loose fitting races in the frame. It was much worse (it tried to kill me on a trip through the mountains) when I had the bike loaded with camping gear and clothes. After I tried all of the above, wheel bearings front and rear, swing arm bearings, etc., which seemed to correct or improve it, I would hit a ripple in the pavement, at some speed, and it would start again.

At last, I hit upon a simple cure. It cost nothing, and I NEVER had the problem again. I moved the Earles swing arm to the front pivot hole, which is supposed to be for sidecar use. Doing this had this effect:
1. The bike did not handle as well at speeds below 10 mph (unless you are into Rally slow race events, at BMW gatherings, who cares?)
2. The overall handling of the bike slowed down just a little bit. Hardly enough to notice.
3. It NEVER shook it head, even when heavily loaded, EVER again.

This is because when you move the pivot axle of the front swingar forward, you are, in effect, increasing the rake of the front wheel, which tends to make the bike want to go in a straight line, and not change direction as easily. This negates the tendency to wobble and corrects for a slight misalignment that may be present in the frame or front end from a slight collision in the past.

...has not solved the problem completely. Next, I will replace the shock absorbers and springs front and back. I would be happy to receive advice on this problem.

On a problem machine, such as yours, I recommend you try moving the pivot to the sidecar position, and give it a try. Riding solo, less a sidecar, with the bike configured this way is not a problem. It saved my life, and I once again trusted the machine in mountains and curves.



Steering Head Bearing Race Removal

Herb Langston writes:

There is a Q&A already for removing swingarm bearing races, which involves welding. Would you recommend this procedure for removing steering head bearing races also?

No, not the steering head races, they come out easily, without such practices. This is from my forthcoming book:

Making the driver to remove the old steering head races from the frame

This is an easy one, and can be made from a cheap, small nail digger, (carpenters refer to them as a sheep's foot) that you can buy at WalMart or a hardware store. The nail digger needs to be a small one, say 12 inches long. On the curved end, you need to utilize your bench grinder to grind the end to a curved knife edge. Use the upper race, which is still in the frame, as your guide as to the proper curve. Grind the end to match the radius curve of the race, and then undercut the side until you create a curved, scraper like edge on the end of the tool. Needless to say, wear eye protection, and keep a pan of water handy to cool the area that you are grinding. You do not want to turn the metal blue and overheat it during this grinding, so quench the end in the water frequently. Depending on the original angle of the end, you may have to use an acetylene torch and heat the tool at the bend, to increase the angle, to allow easier access to the race. Be sure and examine the fit of the tool before you attempt to drive the races out, since there is very little shoulder to catch with the tool.


Replacing Earles Fork Swingarm Bearings

Jeff Yost of Walled Lake, MI writes:

Someone needs to publish a book on what to do when things go amuck during a BMW repair/restoration. I have yet to find a really detailed book that addresses the common maladies that befall us when we work on our bikes. Whenever something happens, I take photos to record the whole frustrating process. However, it is also very rewarding when I can figure out how to overcome a temporary barricade.

I have a book in the works. I'm 85,000 words into it, and no end in sight yet...

I'm reading up on the disassembly of the Earles fork. BMW uses a "Swinging Arm Pilot Bolt", or "Pilot Pin," Matra 519. What is your recommendation for the removal and installation of the front swing armbolt since this tool is no longer available?

Well, the tool is not necessary.

Here is a piece of the book:

Now that you have removed the Earles forks, things are starting to look a bit bare and forlorn, are they not? To disassemble the Earles fork front end, there are two ways to go about it. One is to carefully lay the assembly down, on its side, on an old blanket. That is a bit of a pain, and I prefer to carefully mount the steering stem, well below the threads, in the pipe jaws of a bench vise. This hold the whole assembly steady, and eases the removal of the rest of the parts.

Move the swing arm slowly through it's rotational range. Do you feel any catches, or binding? I thought so. You will need to remove the swing arm bearings, and replace them. These bearings are the same as the wheel bearings in a later /5 and /6 BMW. Shopping list time: The bearing number is a #30203, and they can be bought at any bearing supply or automotive supply house. Might as well buy four, since these bearings are the same ones that are in the rear swing arm. Use a bit of WD40 on the rubber plugs in the spare pivot holes of the fork, and push them out of the holes.

Remove the cap nut from the swing arm pivot shaft, in the left side of the Earles fork (24mm socket). Put the same 24mm socket on the hex end of the pivot shaft, and unscrew the pivot shaft. It is not uncommon for the shaft to resist removal, after the threaded end is withdrawn from the down tube of the Earles fork. You may have to insert a long pin punch into the drilled end of the pivot shaft, and push on the shaft, while you continue to turn the pivot shaft with the socket and ratchet.

Pay attention to the fact there is usually a thin sheet metal shim between the swing arm and down tube. There may be only one on one side or there may be one on each side. Do not misplace these shims, or mix them up, as to which side of the swing arm they where located. You need to mark them left and right accordingly. Now that you have the swing arm removed, lets get the bearings out. Put a flat blade screwdriver into the inner seal spacer, and pry out the spacer and seal. Shopping list time: You should replace this seal during reassembly, and again, you do not have to go to a BMW dealer to obtain it. Any bearing supply house can provide you with a Chicago Rawhide(R) brand seal, and the number of that seal is #8552. Buy yourself four of them, since you will need two of them on the rear swing arm.

Stick your finger into the bearing cone and remove it. There doesn't seem to be any way to remove the swing arm bearing races, does there? The trick is quite simple. Since you are going to repaint all of this, take both swing arms, (front and rear) to a good welder who has a heliarc machine. Get him/her to weld a small continuous bead, all the way around the bearing face of the race, where the rollers used to run. When the race cools after welding, it will simply fall out, by rapping the swing arm on the edge of a wooden work bench. On the rear swing arm, there are two thin plates behind each race. Don't lose them, and don't forget to reinstall them before you put a new race in.

Needless to say, get the races removed before you paint, since the heat of welding will blister and burn the paint. Don't throw one of the old races away, as it will make a dandy driver later on. After removal of the races, be sure and wipe out the hole, and apply a thin coating of wheel bearing grease to the surface that the bearing race seats in, so paint will not stick to this area. After painting, a quick wipe with a rag will remove the paint and grease, allowing you to drive a new race in. During assembly you use the old race, that has been welded on, as a driver. Place it on the new race, and hit the old race with a hammer, to drive the new one into the swing arm.

If you will notice, the threaded end of the pivot axle has an 8mm x 1.25 thread hole in it's center, I use a long 8mm bolt, and thread it into the pivot axle as a guide tool when shoving the pivot axle back through. One trick: If you have had the swing arm out, and you are replacing it back into the "downtubes" of the front end, put the swing arm in place with the shim for the side that you start the pivot axle from. Push the pivot axle through the downtube frame, and through the shim and bearings, and on through the bearing on the opposite side, and then stop. Take the remaining shim and head for the bench grinder. Grind a flat spot on one edge, and then grind that flat to a chisel point. Then, when you are attempting to get the remaining shim in place, between the bearing spacer and front end downtube lug, you will find that a few light raps with a light hammer will drive the shim in place much more easily.

Do not forget that you must preload the new bearings, by tightening the pivot axle. If you fail to do this, you may develop a steering head shake that will make you fill your pants up.

Test the preload by moving the swing arm up and down in it's arc of travel, as you put more tension on the pivot bolt. You want slight drag, but free movement of the swingarm.

What is your recommendation for the removal and installation of the front swing arm bolt? I do not have the Matra 519 tool.

No, it is not necessary... you can use a pin punch to guide the pivot axle through to get it started in the threads.

Lastly, do you use a grease or anti-seize on the bottom threads of each of the shocks (the part that the lower shock support eye screws on)?

You bet... if you would like to ever get them back out again.


Idle Speed Problems

Jon Whittington Writes:

I am having trouble with my 1960 R69 and was wondering if you could help. The right cylinder exhaust pipe is a golden color, and when I pull off the spark plug wire the bike dies. The left cylinder exhaust pipe is shiny chrome and when I pull off the spark plug wire, it will still run on that cylinder.

I can hear the spark popping when I get the left spark plug cap close to the plug. The motorcycle runs well at upper RPM's but does not like to idle very well. Any suggestions, comments, etc. would be greatly appreciated. Thank you.

The first thing you need to check is the compression on the right cylinder. A quick check is to remove both plugs, stick your finger firmly over the plug hole of the right cylinder. Kick the starter pedal and see if it will blow compression out from under your finger. If it does, it probably has enough compression to run. If not, then check the valve lash on that cylinder. It should be .006 on the intake valve, .008 on the exhaust valve, when the engine is COLD, at Top Dead Center, (that's OT on the flywheel).

If you have compression, and it does not run at idle, then more than likely the idle jet or idle circuit is plugged up.

Nevertheless, plugs are strange animals, sometimes they will not fire under compression. I suggest new plugs too. The other source of your probelem can be differential timing between the left and right cylinder. If this conditione exists, one cylinder may be running 5, 10 15 degrees or more being the other, which explains why the engine dies when one plug wire is removed. go here and read this.


Disassembling Earles Front Shocks

Bruce Favaloro wrote:

I'm restoring a '67 R60/2. I've stripped and bead blasted every thing on the bike but the front shock covers. I made a compresser to compress the springs except if I misunderstood what the shop manual was saying I can't get the cover to seperate from top eyelet of the shock to unscrew them. I made sure the hole in my compresser is large enough for the eyelet to clear, but no luck- even almost fully compressed the eye wouldn't seperate. Any suggestions and/or help would be greatly appreciated.

The only thing you have not done is keep the shaft of the shock extended when you compress the spring.

The shoulder of the upper eyelet is sticking to the upper cover from corrosion, more than likely.

After you put your spring compressor on the shock, mount the lower eye of the shock in a vise, and anchor the upper eyelet of the shock by some means (like a steel cable tied to a hook in the ceiling). Then begin compressing the spring. The upper eyelet with then separate from the cover. You will then be able to push the rubber donuts that are on the shock shaft down until you expose the two flats on the shaft. A pair of needlenose vise grips on the shaft flats and a large phillips screwdriver through the eye should allow you to unscrew the eye from the shaft.


Diagnosing Potential Charging Problems

Reggie Smith writes:

I really need your help with a problem on my '60 R69. I have a nagging charging problem that I cannot resolve and apparently the local dealer can't either. My (red) charge light comes on (and really get brighter in 4th gear at speed). It negatively impacts how well my bike runs and I have a noticeable loss of power in 4th gear at higher speeds.

Whoa. Stop right there. Misconception #1. The bike not charging CANNOT effect the way it runs.

The R69, like the other 1951-1969 twins, has a MAGNETO ignition, TOTALLY independent of the charging system. If you are experencing a problem with poor running, missing, or loss of power, you have a problem, but that is NOT from the charging system. That is a different, unrelated problem.

What you have here, is TWO problems, not one.

First, try changing out the plugs, and more importantly at this point, put a new condesor on the magneto. Buy one from a local auto parts dealer, for a V8 Ford. In fact, any condensor will work... but, my field experiments on the subject brought me to the conclusion, (after having an electrical technician that I am buddies with measure the micropharid capacity of the various condensors, along with my rather unscientific method of changing out these same condensors 25 times with various ones for various cars, lawnmowers, motorcycles) that the V8 Ford threw the best visual bright blue spark over a given open air distance.

A failing condensor can cause all sorts of erratic behavior. And, once you cure the problem, alway carry a spare condensor with you. If the condensor fails completely, the bike will not run. Although condensors are relatively cheap, and most people (I for one) won't bother to test one, a condensor can be easily checked to see if these absolute conditions (open or short) are present:

1) remove the condensor from the circuit (i.e. disconnect wire from magneto

2) connect the condensor in series with a 12-volt battery and a small light bulb (do this in the dark)

3) if the light flashes the condensor is working (but may still be weak

4) if the light does not flash then it is open

5) if the light stays on steady then it is shorted

Another possible reason for loss of power could be lack of fuel flow. Check to make sure the petcock is not restricted, and you are getting adequate fuel flow for high speed running.

This condition also drains the charge on my battery- so obviously the battery is providing all or nearly all the electrical charge. Additionally, as the battery charge is drained, my horn no longer works, and my bar-end turn signals don't work if my head light is on. Sometimes my headlight won't even come on. The charge light is dimmer in lower gears, but still comes on.

Reggie, that is because the charging system is not functioning.

The failure of the systen could also be a grounding problem. That is easy to check, though. Solid BROWN color wires are ALWAYS ground wires on a DIN based wiring system. There is SUPPOSED to be a brown wire that attaches to the case of the field. And another to the rear of the trans, not to mention the one in the headlight attached to the switch plate, the one on the negative terminal of the battery, the one running to the taillight, and the one on the headlight bulb. The lighting grounds we can disregard for this discussion.

Here is what has been done so far: I have replaced and charged the battery (Yuasa B38-6A)- no change. I took it to my local dealer and they replaced the generator rotor, brushes, and springs- but still no change.

Another possibilty is that someone was careless during the swapping of components and ruined something...

Finally, they said my voltage regulator was bad, so they replaced the original R69 voltage regulator with a new electronic voltage regulator from Bob's BMW- again, no change. I need your help in a bad way!!! What should I try next and how should I go about it?

How did they know the armature was bad? What made them think so? Did they check for a dead short by putting an ohm meter on one of the copper brush lands, and the other lead of the meter to the engine case? (It should show infinity, an open connection, if it is good. This is not a 100% certain test, however. It is good start, but just a rough test). The only TRUE, correct way to check the armature is with an armature growler. No m/c shop these days would have one. I don't have one either. Only places that rewind/rebuild electric motors would have one. And there is hardly anyone left in the world that rebuilds electric motors these days.

Old Harley's use a 6-volt generator, and there is a chance that perhaps a long-established shop might have one. But most Harley places that I have seen wire the generator up to a battery and see if it will run like an electric motor. If it does, the Harley generator is declared OK. You can't do that to a BMW, for obvious reasons, since it mounts to the crankshaft and is not independent of the engine.

Was there visible damage to the armature? Was it black, or did it smell burnt? Where the wires are soldered to the copper brush lands, is their visible evidence that the solder melted and was slung out of the junctions? If, during the operation of the bike, the original regulator stuck and the generator went to a wide open charge, or there was a DEAD SHORT anywhere in the wiring harness to put a tremendous load on the system (and the charging system is so weak, even when it is in good operating condition, that it will not even melt and smoke the wires- just melt the insulation a bit around the short), the high demand can cause the armature to get hot and melt the solder out of the connections.

Or was there evidence of the armature having touched the field, and scrape marks around the circumference of the armature? You see, if you are not careful, when you bolt the field back onto the gear cover, and do not get the field seated down into the recess of the gearcover straight, the slight cocked angle of the field will be enough for the two parts (field and armature) to touch. If they touch, they will destroy each other in very, very short order.

Examine the inside of the field by removing it. Look for spots where it may have touched. The reason someone may have replaced the armature is that they were careless when they remounted it on the cover, and they ruined the old armature. And they may have unknowingly ruined the field too. In the armature they replaced, was the replacement new or used? You must be careful, because there are TWO different wattage generators. They both look identical, in the fields and the armatures of each. But if you mismatch the parts, i.e. use a 45-watt armature with a 55-watt field, it will not charge.

This sort of problem is difficult for me to help you with, since I am here and you are there, and I can't look at it. But, I would suggest that you get the old armature back and examine it for physical damage.

If you see no physical damage to the armature and the inside of the field, reinstall the original armature and put it all back together and try it with the new regulator. Get the installation instructions for the regulator and double-check to see that it is wired in correctly. 90% of the time, failure of the charging system in these bikes is the voltage regulator. That is the FIRST thing I recommend testing or swapping out. Obviously, it is much easier to replace the regulator with the field removed from the bike. However, a careless mistake in the reinstallation can destroy other components. I'm afraid that due to the lack of diagnostic tools, such as a growler, one must resort to component swapping to fix the problem.

In my experence, in the remaining 10% of the time, the field or the armature do indeed fail. A rough check of the field can be done by removing it, removing the wires

that connect the series of coils to the terminals on the face of the field, and then, by using an ohm meter, check the resistance of each individual field winding. I cannot recall, without the factory manual with me, what the resistance value is of each individual coil. But simply compare the values of each one, and you can determine if you have an open circuit, dead short (low resistance or no resistance), or if the values are pretty much the same on each one, and there is continuity through all four, which is good.

Do this check with all the field coils in place. Do NOT be tempted to remove them from the field. Their north-south orientation in relation to one another is critical for the generator to charge. Also, it is very easy to get one of the coils slightly missaligned in relation to the housing, which will result in the winding touching the armature during operation. There is nothing wrong with the solid state regulators, I use them regularly as replacements, and they work fine. The only way they can be carelessly destroyed is by hooking up the battery backwards.

Hope this sheds some light (of a 6-volt nature) on your problem... :)

By the way, you can replace the whole 6-volt system with a 12-volt Alternator. There is currently a conversion kit, and while it requires the mounting of a diode board and voltage regulator under the tank, an adapter ring, additional wiring to the bike, and of course the replacement of all the bulbs, it works GREAT and you can SEE at night!

Also, VERY soon I will be testing a prototype, 12-volt alternator that will have a built-in voltage regulator and diode board, and will require NO modifications to the wiring harness, NO additional wires, and NO adapter ring. I intend to do a review of this new system for the next Vintage Bulletin.

Try these suggestions, and get back to me with the results.


Loose Kickstart Lever

Mack McKinney asks:

Where could I find out how to tighten the kickstart lever properly on my '62 R60? It stays loose. Thanks.

There can be several things wrong:

1) The D-shaped pin that holds the lever to the shaft is ruined from not being pulled up tight enough the last time someone had it off.

2) With the lever loose, it may have distorted the flat groove in the shaft that the flat side of the D-pin locates on.

3) The nut on the D-pin just may not be pulled down tight enough to seat the pin.

If you have tried tightening the nut on the pin, and it is still loose, back the nut off until it is flush with the end of the pin. Get a brass drift/punch and a hammer, and drive the pin most of the way out, then take the nut off and drive the pin out the rest of the way. You will probably see the that the pin flat is distorted badly. Replace the pin with a new one, taking care that you have the pin oriented so the flat side of the pin will contact the groove in the shaft.


Magneto Coil vs. Coil and Breaker Ignition

rharms1 writes:

As discussed ad nauseum magneto coils and those used for coil and breaker ignitions are fundamentally different. On the /2 they have been of indifferent quality and expensive. While there appears to be "good" ones available now they are quite expensive.

I suppose it is all relative. $160 is the current price on the "good" coils, and that is around $45 cheaper than some of the "not so good" reproduction coils of the past.

These tractor sites list new magneto coils in the 40.00 dollar range. Haven't tried any of them. Don't know if they would fit, etc. Just food for thought.

Trouble with the BMW coil design are twofold:

1) There are TWO independent coils in one unit.

2) Due to the design of the magneto, the linear speed of the magnet, from which all of the strengh of the spark is derived, is very, very low compared to other magneto systems, such as one in a lawn mower, which has the permanent magnet mounted on the outside edge of a large flywheel, giving it a very high speed linear movement.

I played this game many, many times, trying to find a coil that would fire in place of the original type. I did find some that would work (from aircraft engines) as long as the shaft speed of the magnet was kept high. Trouble was, when you allowed the engine to drop down below 1000 rpm, it would quit running. And there was NO way you could kick start it. You had to drag the bike down the street and pop the clutch to get enough speed to create a spark.

The BMW coil has many, many more windings in it to compensate for the lower linear speed of the magnet.

I doubt there is another coil out there that has that number of windings to compensate for the very low linear speed of the magnet. Remember, on a BMW the magnet is turning at 1/2 the speed of the crankshaft, and is very close to the center of rotation of the cam, hence the low linear speed.


Removing the Steering Stem Lock

A quick little tech tip, for those who have lost the key for the frame/steering lock on an airhead, can't find a key blank, and want to remove the lock, to replace the whole thing with a new lock and key set.

1. Take two small screwdrivers, and drive each one under the Neiman chrome lock cover, on each side of the retaining rivet. Pry the cover up, and remove it alony with the rivet.

2. When you look at the end of the lock, you will see the round barrel of the lock, with the key slot, and square box, on the top. that box is where the tumblers and springs of the lock are located. On the top of that square
block, there is a thin band of sheet metal, that retains the springs and tumblers. Use an ice pick to lever the plate out, so you can grab the end of it with a pair of needle nose pliers.

3. Remove the plate completely, and you will notice that the ends of 4 springs, that push the tumblers down, into the lock, will jump up and their ends will be visible in the small open area directly above the lock. Bend
yourself a small hook, out of piano wire, and reach into this area, snag each spring, and pull it out of the body of the lock.

4. Insert a flat blade screwdriver into the key slot, and use a light hammer to drive the screwdriver into the slot. Don't go crazy here, just drive it in enough that it will stick in the slot.

5. use a blow gun on a air line from an air compressor, and blow air into the key slot. This will push all four of the tumblers up, out of the lock. While you are constantly blowing the air into the lock, turn the screwdriver
in a counter clockwise direction, and the lock will rotate. When you have it rotated, simply pull the screw driver out, and the body of the fork lock will come out of the frame, on the end of the screwdriver.

Simple Eh?

That is how I have removed them in /2's for years.

Q. Is there anyone repairing bar end turn signals when the expansion area cracks off?

A. Not to my knowledge. I have saved broken ones, by drilling a small hole through the handlebar, and into the body of the bar end signal, and then taping the hole and using a set screw to retain them. It works. You must be sure the set screw does not protrude above the surface of the bar.

Q. How do you tell cheap signal copies from the authentic Hella brand signals?

A. Real ones come in a bright yellow box with Hella logos printed in blue. Original signals have "Hella" cast in the yellow lens. The fakes signals don't have a cast boss (raised square area) that fits into a notch you must cut into the handle bar to fit it, keep it from rotating. Real Hella signals have a small terminal block inside with a set screw to attach the wire to the terminal block. Fake signals have the wire hard-soldered in and a short length of wire sticks out of the end of the signal.

Q. Can you patch holes in petcock bodies?

A. Not to my knowledge. I have had limited success using low-temperature propane torch rods for "welding" aluminum and pot metal that J.C. Whitney and Eastwood Supply sells. I say limited, for pot metal is tricky. Too hot, and the whole thing melts, without warning.