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Repair, replace and adjust BMW motorcycle controls and cables |
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1. Castings and handlebar levers. a. Basic throttle cable adjustment of the /2 B. Front brake and clutch cables a. Removing a /2 cable at the top end C. Riding with no clutch cable IntroductionThis page has grown like cancer. It started out very small and is over 6 times what I had anticipated. It is no longer my page, but a compilation of ideas, tips and photos of many people. I try to give credit, but it is impossible now. I have gotten a great response and many are similar or even exactly the same. I have tried to give credit to the first one received. All are appreciated and have contributed to the overall success of what you are about to read. 1. Castings and levers The castings for both throttle and clutch are a cast aluminum, sort of a high quality "pot" metal. All were spray painted a gloss black. They fit only 22 mm diameter handle bars. 22 mm equals .866" and the American 7/8" equals .875." Never try to slide them over an American 7/8" sized bar. The casting usually breaks and it is very expensive to replace. I measured eight 22 mm bars, spanning 25 years and found a wide range. The older ones were .862" to .866" and the newer ones up to .868." The only 7/8" bar I have to measure is .878," or a bit big. I used to import bars from Magura directly and they had another "defect." It was in the bending. By turning the bars over and laying them flat on a glass plate, they often would "rock" a bit. If your bar rocks slightly, it may be within the norm. The bar could be off by as far as 1/8." It seems that the quality control isn't very good on either the handlebar bends or the tubing diameter. Sometimes the casting resists going over a 22 mm bar. I use a flat blade screw driver, as a wedge, to slightly open up the "pinch" part of the casting. Don't try this on a 7/8" bar.
Don't use any lubricant on the bar to install the casting. Have the bar and inside of the casting clean. Check the bar for nicks that stop the casting from sliding on freely. Dress them with a file or stone. The throttle tube may get lubed later, more below. One of the most important items to check for on your control is the perch wedge. This part is what keeps the casting from rotating on the bar. Use of some nonstandard piece of metal may not "bite" into the bar. This will require that pinch screw to be tightened up more than desirable. I actually prefer to tighten it up so that it will rotate with a strong twist. I keep the casting tight enough that it doesn't move with normal use. My reasoning is that if the bike falls over, or worse, the casting will have a chance to rotate. That is much better than bending or breaking the lever. A. Casting position The casting position is fairly important for comfort and safety. If the lever is too high, it is very hard to pull it in the downwards direction. It can make you sore from frequent use, especially when riding in city traffic. It also takes too long to reach it, so safety is an issue. If the lever is too low then again it is harder to pull. It is probably less distance for your fingers to travel in a panic, so the time may be shorter. I prefer perfectly adjusted castings. If you draw a line from your shoulder and through the handle bar, it should also go through the lever. Another way of saying it is that the levers must be pulled directly towards your shoulders. Pulling "down" or "up" is making your body work harder.
Your arm and extended fingers on the lever should look about like this. B. Levers Since before the war, BMW has used Magura levers for almost everything. They were, and may still be, the highest quality lever on any machine. I have, on occasion, been able to straighten one that is bent almost double. It is easy to straighten one that is bent at only 90 degrees. Use the characteristic of "cold flow" that some alloys exhibit. Mark Huggett tells me that the levers are made of a die cast zinc.
I use a pipe to go over the lever and a hammer handle to go in between the bent lever and the grip. Move it very slowly. I suspect that it is safer on a warm day. It would take at least 15 minutes to fix one that is badly bent. Sometimes I get bored, quit and come back later to do more bending. I have only seen levers break, when in a sharp kink or get straightened too quickly. When the bike fell, the lever got bent almost instantly, not slowly. It seems that it can take one fast bend and maybe no more. If one breaks off, maybe it has been straightened once already. A few times I have straightened a lever more than once. The lever ends can be filed down to get rid of minor road rash. Magura levers are mounted with a very thin wave washer to reduce vibration. The washer can go on the top or bottom of the lever. It fits in between the control casting and the lever. A lever with the ball end, finger grooves and washer can be seen here. The levers have changed slightly over the years. Before 1965 they had pointed plain levers. In 1965 BMW introduced finger grooves and a ball end for safety. In 1978, I think, they changed the line to have a "dog leg" and no finger grooves, for more comfort. The lever needs to be lubricated from time to time. A drop of oil from the dip stick is enough. A variety of castings have been used over the years. Some have a hole for a mirror and some are plain. The clutch side mirror hole is a left hand thread. That way, the wind pressure tends to keep it tight. The throttle side has a right hand thread. C. Switches Many types of high beam switches have been used, one typical for the USA and the others for the rest of the world. When the Earles fork models came out in late 1955, no turn signal provision was available. Some owners made up turn signals to suit. I don't know the exact year that the now famous bar end turn signals were made available. Could someone tell me? I "think" it was around 1958-60. A new BMW would come with one of two throttle castings shown below.
No flat Typical flat On the throttle side a "flat" was machined in for mounting the turn signal switch. The stock rubber grip came in two types. The older one had the rubber cast over the end for bikes without turn signals. One could cut a hole in it for the turn signals. BMW also made one with the holes cut into the ends. Later on, mid 60's, BMW had only the one with a hole cut in the end and the plastic cap covering the hole. Retro fitting turn signals onto older BMWs.Here is what I think happened, but I don't know for sure. I would certainly entertain a different opinion, or information. BMW offered up a kit to retro fit the bar end turn signals onto the older bikes. A template was with the kit for drilling two holes in the throttle casting. That made a place to mount the "adapter" piece that would allow the mounting of the turn signal switch. A variety of switches were used and I recall at least three different ones. These next 4 photos were provided by Dave in Michigan, thanks.
This is the finished product
The switch is removed to show the adapter mounted on the casting. The screw is not original, as no Phillips were used in the production of the early bikes.
The adapter with mounting screw. The switch mounts in two places. It "hooks" at the top and a screw is used at the bottom, same as the usual USA switch on the left side.
This photo shows the two holes that were drilled into the casting for mounting the adapter. From a close examination of the casting, it appears to have some cast in "dents" above the main hole for helping locate the adapter. This suggests to me that this may have been cast by Magura just for this switch adapter. I do not recall ever seeing this. The ones I saw were done by the owner or mechanic probably by using the template. Within the past year or so I sold one on eBay. If the buyer reads this, please contact me, as I would love a picture. Generic switchThe number of motorcycle manufacturers in central Europe was quite large. Many used Bosch, or Hella electrical accessories. A switch was provided that could be used for turn signals and fit directly on the handle bars. This made it hard to reach and I saw very few of them.
The adapter is mounted on the usual switch. Photo from Ash, thanks. Another type of switch
Picture donated by Dale Thomas, thanks This switch is a bit unusual and I have only seen a few. It is mounted on the left side and serves as (top to bottom) High/low selector, horn and high beam flasher. The high beam flasher works even if the headlight is off, as in the daytime. Europeans use it to warn slower vehicles that one is approaching and please move over to the right. Front brake switchUntil about 1954 BMW didn't even provide a switch for the rear brake. In 1968, or 69, the state of California required that the front brake switch the brake light. That way either brake would show that the bike is stopping. I seem to remember that the very first of the US models didn't have the front brake switch. Does anybody have an early US model without the brake switch? Does anybody have a 68 model with Earles forks without the front brake switch?
This is the switch shown on a /5, but it is the same for a US fork model. The switch has the rubber dust cover removed and this one has no wiring hooked up. Notice the corrosion on the terminals. Clutch switch
This photo shows the same switch on the clutch side. It made the rider pull the clutch lever in, or be in neutral, before the starter would engage. The same brake switch was used on the clutch side in 74 only. For 75 they went to a smaller one.
BMW used this switch from 75 on.
2. Cables The cables used by BMW are of high quality. A cable developed by a Brit. named Bowden, called "Bowden cable" in German parts books, consists of an outer sheath, or jacket, in black, made of some plastic. Next is a metal spiral that is the outside part of the "working part" of the cable. Being made as a spiral, it can flex easily. The spiral must not be "compressible." Next is the inner "wire" which is the pulling part. It must not be "stretchable." I understand that today's clutch, front brake and throttle cables have a Teflon liner between the wire and spiral to reduce friction. These newer cables must not be lubricated. The storage and packaging of cables can affect their operation. You probably have seen some shops store cables by hanging them vertically on some type of rack. That is, by far, the best way to do it. I was disturbed to find more and more cables arriving in prepackaged shrink wrap with the cables all coiled up. Time spent in a coil will give them a "set." That set is the spiral being pulled apart. When you get your spare cable, be sure to store it not coiled up. It can hang or lay flat. A quick test of a cable is to let it hang vertically. The inner part should almost drop from gravity. At most it should only take a very gently touch to lift it or push it down. This takes some experience so don't throw away a cable based on this. Start "testing" every cable you come across, just to learn. A throttle cable that has significant resistance will cause tuning trouble. Replace them. If you need cables of a special length they can be custom ordered or built in your workshop. I have repaired and made up many cables. Flanders used to sell kits of quality cable ends for those wishing to make cables. Do they still? Does someone else provide them? A. Throttle cables The throttle cables are extremely reliable. I have seen them break from an accident. I saw one, on a /2, last so long that where the little ferrule was fastened onto the cable at the carb end, in the slide, it wore down to the point that it pulled through and would no longer work. (see notes below) I have seen them seize/rust up from sitting out in the rain for a few years. I have never seen a /2 throttle cable break from old age. The first reason that we would replace them is that the outside metal spiral would get stretched and become a "spring." That spring would compress and make synchronization impossible. One carb would get it's slide lifted and the other wouldn't start till the spring got compressed. Even worse is that they might start lifting at the same time and as the needed tension increased, one would began compressing the spring while the other side was lifting. Mid range would be "out" but the start of the throttle would be correct. Great fun to figure out what is wrong. The result is vibration, because at some part of the rpm range, one side is doing too much work. An inspection of the cables will reveal the "stretch," example shown below. Always replace them as a pair. The second reason is that they had too much resistance and would cause trouble with getting the engine back to a consistent idle rpm. First we would try some lube and that often fixed them, but these later lined cables are not to be lubed.
If you look very carefully, some of the jacket is failing to cover the spiral. At the top of the spiral a reflection of light can be seen that is between adjoining wraps of the spiral. That reflection is off of the wire inside. We shouldn't be able to see the wire. When the throttle is opened, the tension on the wire will cause the spiral to try to compress. It acts as a spring and will compress a bit. If the other side carb is exactly the same, it won't matter at all. Both could compress at the same rate and the carb sync would be OK. That isn't likely though. Most likely is that one side will compress more than the other and that side will be slightly behind the "tight" side. This throttle cable isn't very bad and I wouldn't replace it yet. I just didn't have a really good example of a bad cable. This small error occurred because the cable has a slight bend just at the adjuster. You can see it. Over time the spiral has taken on a set with one or two spirals spread apart slightly. I have seen 1/2" spread and more wire showing between each wrap. In that case the carbs just can't be brought into sync. Routing Cables would last the longest if they pulled completely straight, but they can't. The more gentle the curve, the less drag, longer life and the easier lever pull it will have. I would love to tell you how to route them, but that is not always possible. Due to variations in bars, tanks and other accessories, one must figure it out for that specific bike. Keep all cables a bit away from the coil connections on the /5 and later. The push-on connections can rub through the plastic jacket and short the ignition system. That happened on our race bike, and yes, in a race. We saw it on a few customer's bikes too. After you find a successful path, tie wrap them gently to the frame back bone, so they won't move easily. BMW uses a unique system for pulling on the throttle cable. It provides a straight pull at the control end. No other company, of that era, had a system nearly as good. It uses a bevel gear drive to pull on a small piece of chain. Other companies allowed the cable to wrap around the bar and each throttle opening it flexed some. Eventually it would break. This bevel gear system is more expensive, but with proper lubrication will last almost forever. It does require some adjustment that is a bit strange the first time that an owner does it.
The brass gear is turned over to show what it looks like. Look carefully at the lower teeth and see some wear. That one is still useable, but not great. The tube shows no such wear. This brass gear is for the /2. The /5 had a cast pot metal gear. This wasn't a set, just some old parts that I could find for the photo. The bevel gear isn't a linear pull system. It is made in such a way that the first few degrees of twist, it only pulls a small amount. During the mid to upper range it pulls much faster. This gives you precise control of rpm at the lower end. I mention this because this (sort of) requires the bike to be adjusted in a certain way. It is all easy, but not obvious at first. a. Basic throttle cable adjustment for the /2 The /2 and /5 have almost identical throttle assemblies. The /2 has no special markings on the gear teeth like the /5. In that aspect, the /5 is slightly easier. If your /5 has good cables and you want to apply this procedure, go ahead. These directions assume that the cables are not stretched or made with too much wire sticking out. You can't know that, so proceed and see what happens. You are not going to get into trouble. If one, or both, of the cables are "stretched" then it will be impossible to synchronize them correctly.
Rubber boot Slide the rubber boot up and off of both carbs at the cable adjuster. Only the slide carbs have this rubber boot. The CV carbs don't have it as they don't need it. More on this later. Both of the adjustments probably looks like this.
They should have the same amount of threads showing. If not, then one cable "inner wire" is too long. You can tolerate some difference, but if you find one adjuster all of the way down and the other one almost out of threads, buy new cables.
They should look like this, so adjust them till they do. I like to have one thread up from the bottom, it gives me some "play" room. More on this later. I would consider them ideal of they both look like this. Note from Mark Huggett. The carb tops displayed above are original and require a right and left. Now BMW provides a universal top with a screw in brass fitting that can be rotated to adapt to each side. The problem is that this brass arm is 10 mm longer than the original and this takes away from the free play. Magura throttle gear adjustment on the BMW motorcycleNow the throttle cables have some play. The play has been increased by the amount that you turned the adjusters down. We will now "fix" it at the top end. This involves a rather clumsy operation the first time, but would seem easy if you were to do it several times in one day. You may have that chance, especially since this is your first time, but we hope not. The /2 and /5 have marks to show the proper teeth matching. The reason that this is important is because the brass gear is a cam. It pulls on the cables slowly at first and at a higher rate as the throttle approaches 1/2 or more throttle. This is designed to allow the amount of opening to be carefully controlled by the rider at lower rpm. At slow speeds the amount of power can be easily controlled. At higher settings it will open faster. While this is nice in theory, one does have some amount of adjustment in the teeth to use for proper control of the slack in the cables. It is more important to have the cable slack taken up fully by the bevel gears than to allow it to remain. Feel the throttle "play" or looseness that is now evident. Remember this amount of play. Turn the throttle grip just up to the point where it would start to pull on the cables. 1. Remove the screw holding the throttle cap. The /5 and later have a rubber boot to keep dirt out. It must be slide back quite a ways to allow this next operation.
At this time you could use a short-cut and leave the screw in only one thread. Lift the cover in the right side and it will look like this.
Now drop down to step #7 and proceed. I recommend going through the whole thing at least once. You will learn more and also assure proper lubrication.
2. Pull the upper throttle cable, with your left hand, back (to the left) until you see the wire, like this. The lower cable is "captured" and can't jump out. 3. Very carefully lift and wiggle the cap up and off, being sure to not let anything move. The throttle cable ends can come out easily, so be careful. It isn't a disaster, only a nuisance.
You may now relax the throttle cable in your left hand. The cap has a hole for the outside of the cable to hold it in place. The slot for the cable wire is so small that one can only get the wire through. That is why the cable must be pulled back. Understand this part, it is important and you will use it later. 4. Make sure that the bevel gear area is well greased. Clean out old dry grease. Make sure that you grease the channel that the pull block runs in too. Use any thin grease. The grease will need to be checked again in a few years. 5. During normal operation the throttle grip tube won't come off of the handle bars.
The tube has a slot in it like this. The cap tang. 6. The cap that you just removed has a "tang" that sticks down into that slot.
The photo above is what you would see if the casting were invisible. The cap holds the throttle grip tube from coming off. 7. With the top removed, the grip can be pulled out, to the right.
Only pull it out enough to unmesh the teeth of the bevel gear drive mechanism of the throttle. It is only about 1/8" or so. On the /2 there is a spiral spring inside the tube at the outer end.
Photo of the /2 spiral spring, by Bernd Kupper, thanks The purpose of the spring is to provide resistance from the grip easily returning to idle. It is a crude "cruise control." It's tension is only adjustable by the amount of grease, or lack of grease between it and the bar. You don't want to allow it to come off of the bar. If it does, it isn't the end of the world, but now it must be started back on. That takes a turn in the wrong way to allow it to "walk" onto the bar. The /5 and later don't have this feature. They have an adjustable throttle screw as a type of "cruise control."
The screw with the spring around it and underneath the control is the /5 and later "cruise control."
This is what the part looks like. The spring is "captured" on the screw. The white plastic is what rubs against the throttle tube to provide the drag. This part can fall off and we sold lots of them. Just loosen it enough that it no longer provides friction and it won't fall off. 8. Turn the grip in the idle direction. The amount is the amount of play that you were told to remember at the start of this. Gently shove the grip back into the casting so that the teeth mesh again. Again, as in step 2, pull the top throttle cable back. Replace the cover and gently wiggle it so that it sets down into the slot in the throttle tube. Relax the top cable so that it fits into the hole in the cap. You don't need the screw yet. Hold the cover down and test the throttle grip for play, it should be very little. If it is still too much, repeat steps, starting at #2 and try to catch the next tooth. The amount of play that one tooth will take up is about 1/8" at the grip. You can't usually get all of the play out, only most of it. The lower adjustment can easily take up any residual play. Replace the screw. Leave the throttle fully in the idle position. 9. The cables are now out of synchronization. Basic sync is very easy. Grab one cable at the carb and gently pull on it. You should be able to feel the play. Rotate the adjuster out to where there is about one thread of play. You must leave some play. Adjust the other cable. 10. Start the engine and let it warm up a bit. This next step takes two people. Have your helper very gently turn the grip just barely off of idle. You go to the rear of the bike and lean over and put your head up to the rear fender. Make sure that you are centered. Make sure that you can hear with both ears. As the throttle comes off of idle, one side may pick up first. The stereo affect will make it obvious. Go to the other carb (the one that didn't respond or did so later) and turn the adjuster out a bit. Test again and adjust as necessary. This is an alternate method and doesn't require the extra person. With the bike warm and idling, bring the adjuster up until it just starts to pick up the slide (increase the rpm) stop and adjust it back down one turn to give some slack. Do the other side exactly the same way and amount of slack. This will get you extremely close and good enough for most of us. Now that you are happy with the sync, here is a very important test. Turn the handle bars from side to side and watch for any change in the idle speed. You might need more "slack" or "free play" in the cables to prevent the bars from affecting the speed. You might need to reroute the cables to fix it. 11. Now you have the basic sync done and it may be enough for you. Don't use the wrench to tighten the locking nut. It is not only unnecessary, but I have seen the threads pulled out of the carb top. Use only your fingers to tighten it. First, do your best with fingers on the nut while holding the adjuster. Then, grab both adjuster and nut and tighten both. Yes, you will slightly alter the sync, but it will be the same amount on both sides. Do the other side too. If you need to adjust it again after a few days or miles, you don't need a wrench, just your fingers. It won't "creep" as you ride. 12. If your bike is one with the boot on the cable, as on all /2 and later slide carbs, it is time to move it down again. The purpose of the boot is to try to seal off air and water. Notice how very tight it is? As you push it down, also rotate it for ease in getting over the carb top. Once it is in place you are not finished. You must rotate it to let it extend again. As it got pushed down, it gets fatter and shorter. When you release it, the thing wants to grip the cable and lift it up. This will mess up your sync. I have never noticed a mixture change from the boot being "up" or "down." My fear of air leaking into the carb via the cable is long gone. I use another modification. I cut off the lower neck of the boot. This allows it to move up and down without grabbing the carb top. The rain is kept out, as before, but now the boot has no chance to mess up the carb sync. It is now easy to slide the boot up, adjust the cable and slide the boot down again, all with no tools. 13. You may have a vibration at road speed that you suspect may be the sync. It is possible for the slides to lift off in perfect sync and then be out of sync at some road speed. Here is one way to deal with it. Loosen the cable adjuster lock nut on the left side. Warm up the bike and take it up to the speed that you suspect may be out of sync. With your right hand holding a steady speed, reach down with your left and slightly turn the cable adjuster, one way and then the other way. Judge by vibration changes any difference. The vibration in the mirror may be a great indicator. You could leave it at the place where the vibration is the least. You will probably find that the idle won't lift off equally as you previously adjusted at step # 10. You must decide which is more important to you, slightly less vibration at road speed or smoother "pick up" off of idle. It has been mentioned that riding with one hand may put you at risk for a wobble. That is true, but the bike has a really big problem if it is that unstable. 14. If #10 and #13 give drastically different results, go through them again. If that is the best it gets, then go to my page on tuning to read more about possible factors. 15. Another method has been used by shops and some owners with some success. It was used in my shop with some success. My best mechanic, Bryan Hilton, didn't like it. The idea is that if each cylinder runs, by itself, at the same rpm, above full advance, the two will put out equal horsepower. While it may get you in the ballpark, it assumes to many things that may not be true. This method takes some practice, skill and a large fan for cooling the cylinders while doing it. An experienced mechanic can do this whole thing in under two minutes. It involves removing the spark plug caps and inserting an extension. The extension is home made. I am told that Ed Korn sells this tool as a set of two. It is nothing more than a 3" long threaded rod with the ends to conveniently mount it. The top end uses a spark plug round threaded thingy and the bottom end has an end like in the spark plug cap. The purpose of this extension is to expose the spark plug voltage. It is now easy to "short out" the high voltage ignition. It will kill that cylinder. The mechanic runs the rpm up to what is needed to achieve full advance with one plug shorted out. Watch the rpm. Quickly un-short that one and short the other one, note the rpm. The cables are then adjusted to achieve equal rpm. Caution: the throttle is so far open that you must not let it run on both cylinders at the same time, or it could go past red line. Personally, I don't recommend this procedure for the casual owner. The accessory electronic ignition systems for the /5 and later are working out well for owners. It has been suggested that those systems don't like to have a spark plug shorted out. 16. The R75/5 throttle cables must come straight up for some distance from the carb. If it immediately bends over towards the underside of the tank, it can affect the sync. I have seen owners tie wrap the cable to the spark plug wire to keep it vertical. Warning on /2 BMW throttle cablesA note on new throttle cables. BMW is selling throttle cables with crimped on, square ends. These are crap as they are *just* a couple (not few) thousandths of an inch larger than the square slot in a Bing slide. If the cable slot in your slides are even slightly worn, the cable will pull through. I'm not the only person on this list who, when we've complained about it, have been told "Your slides are worn out." I just heard from Mark Huggett huggett@bmwbike.com that BMW is aware of this defect and is in the process of changing it. It is hoped to be "fixed" in the next few months. Mark is a supplier of BMW parts from Europe with good prices reported B. Front brake and clutch cables The front brake and clutch cables on the /2 and /5 do break. They usually break at the top end and it is due to lack of maintenance. The lower ends of both are a straight pull and not subject to bending, like at the top, at the controls. The break is within about the first 1/2" (5-15 mm) of the barrel. The barrel begins to not rotate freely in the lever due to lack of oil. To inspect it is very easy. Slowly pull the lever and watch the wire that is now exposed. It should move freely and not in small jerks. The jerks show that the barrel is sticking in the lever. The wire bends slightly to accommodate the stuck barrel. That bending is what finally causes it to break. One drop of oil is enough to fix it. Depending upon the weather and amount of riding in the rain, will determine how often to do it. a. Removing a /2 cable at the top end. This one is so easy, but somehow it seems to be largely unknown. This works for either the clutch or brake cable. I will use the clutch as an example in the photos. Loosen the aluminum lock nut, run the brass adjuster all of the way in and line up the cut out parts with the slot in the casting.
See the section that was cut out to make room for the cable? All three slots are lined up. Pull the lever all of the way back. Grab the outer sheath of the cable in your right hand and pull. Now slowly release the lever and your right hand will seem to pull the outer sheath away from the adjuster. It will look like this.
The cable pulled out of the adjuster Now the cable can be taken out through the lined up slots. It will look like this
Remove the cable by dropping it downwards and out of the lever pivot. To install it again is sort of a reverse procedure. Hook the outer sheath on the adjuster locking nut and pull the lever. It will look like this.
Slowly release the clutch lever while pulling with your right hand. The cable sheath will follow it, as before, giving you the slack necessary to rotate the wire back through the slot and in place. Release the cable and adjust the adjuster as needed. This adjustment should only be about one turn out. Any extra slack should be adjusted at the bottom end. This way you can easily change (tighten up) the adjustment as the cable stretches out. b. Removing and installing the /5 and later clutch cable The /5 uses a slightly different system from the /2 and it takes a bit more work. The advantage of the /5 system is that the upper cable end is completely covered and stays clean and dry. The /2 can collect dirt and that causes wear. I much prefer the /2 system as it is easier to adjust, lube, change and inspect. The /5 (and later) clutch cable must first be removed at the lower end.
This is looking up, from below the exhaust pipe, at the clutch arm and cable. This is the place where it must first be removed. It can be done in two ways; fast or slow. You can also see the center stand spring for a Reynolds Ride Off Stand.
The slow way. This is looking at the adjustment bolt and locking nut for the gross clutch cable adjustment. See the 13 mm locking nut? Loosen that and then back off a turn or two on the 10 mm adjuster. The faster way below.
I have stuck a lever behind the clutch arm and levered it forwards. This will easily give enough slack to reach in with your right hand and drop the cable off of the arm. Now the clutch cable is loose at the lower end. At the lower end shove the wire fully in towards the sheath, which is towards the upper end. This will give enough slack at the hand clutch lever to pull the barrel retainer out.
This is the upper end of the clutch cable with the retainer in place. You can't see this on the bike because it is all inside of the clutch casting and lever. This is to only show you what you are trying to remove. The round thing is the barrel retainer. The slot that you see is too narrow to allow the retainer to be pulled out. That is why you are getting all of this slack described above.
The photo shows how it looks with enough slack. The wire will allow the barrel retainer to be pulled down and out. Now the clutch cable is loose at both ends. You want to replace it? I can't give you the full procedure because each combination of tanks, bars and accessories make it custom. You will need to thread it down and along the right side of the frame. It is a bit tricky at the back end.
This is what the installed cable looks like at the transmission housing. This is the part "boss" that holds the sheath from moving. Some difficulty may be encountered when trying to thread the wire with the accordion boot around the boss. The cable end and boot can be run down and in between the transmission and the frame. Then move it back and under the boss. Then you will be able to finish installing it. It is the reverse procedure. Be careful to not allow the barrel retainer to drop out and get lost on the floor. The new cable will need to be adjusted with the lock nut and adjuster. Run the 10 mm bolt adjuster in a few turns with your fingers. Stop when it starts to get tight. Try the clutch hand lever for the feel of slack. Adjust as necessary and tighten the lock nut.
You should end up with about this much "slack" or "free play" in the clutch lever. BMW motorcycle clutch adjustment for the pre-1981 clutchThere is nothing hard about adjusting the clutch cable. It is really simple and can be done a variety of ways. The end result must still be the same. One must end up with a bit of free play at the top end at the lever. First off, lets understand that both the top adjustment (hand lever) and the lower adjustment at the transmission do exactly the same thing, as far as adjustment goes. The lower one is "gross" and the upper one is "fine". One turn on the bottom is about equal to 6 turns on the top. That is from memory, so don't get upset if you measure it and find a different number. I am just trying to show the relationship between them. Because BMW used a couple of variations in clutch parts, they ended up with a few different traits. My simple method takes them into account.
1. When all is said and done, one "should" have the upper adjustment "out" about 2-3 turns. This allows one to easily "run it in" a couple of threads to free up the adjustment for a really hot run when the clutch heats up a bit. This does not happen to all BMW clutches, or all hard riding, but it does happen to some and I allow for it. I suggest that you do too. This way, you have adjustment in both directions at your finger tips. 2. Once the upper adjustment is set, then finish with the lower one. Run it in by hand until you feel some resistance and then lock it down with the nut. You may need to hold the bolt with a wrench while tightening the lock nut. 3. The adjustment should be in the ballpark, so check it. One should find "that bit" of free play. Where and how you measure it is not important, but free play must be there. If you measure the ball end tip of the hand lever, then it is about 1/4" to 3/8" or a cm or so. Too much would be 1/2" to 3/4" and 1/8" would be too little. Too little and one runs the risk of it tightening up and not fully engaging and then slipping. Too much free play and one runs the risk of not fully disengaging. That will make shifting difficult. You may need to go back and make a small adjustment to get it right. See the next two photos above. A properly operating BMW motorcycle clutch will not start to engage until the hand lever is out past 1/2 way. The area where it starts to engage and finishes is very small and about 3/4 of the way out. THAT IS NORMAL.
When you see the adjustment at the top with the adjustable barrel almost all of the way out, it is past time to fix it. It very well could have the proper free play and work perfectly, but one has lost the ability to make a fast adjustment. This applies to both the clutch and front brake. Improving the very "hard to pull" /6 BMW motorcycle clutch lever.This mod will work on just about any BMW. I did about the same thing on my VW powered BMW in 67. In 1974, with the advent of the /6, BMWs clutch pull was excessive, to say the least. Almost instantly people came out with various fixes. This is one of them. It doesn't require cutting the original clutch cable and is therefore superior to some that require cutting the cable. It is by "Catch" and can be seen at http://www.frankhams.freeserve.co.uk/temporary_uploads/ezclutch_page.htm I hope that they keep this page up for some time. Another web site that deals with this issue is http://www.bmwman.biz/ and between the two, you may decide to do it. You might take a look at this one too, http://www.trengaracing.com/catalog/product_info.php?cPath=31&products_id=153 Vech at Bench Mark Works also has a similar product. C. Riding with no clutch cableIf the clutch cable breaks while riding, it is due to lack of maintenance and inspection. When it happens you have the chance of that retainer falling out and getting lost on the road. If you carry a spare clutch cable, I suggest that you also carry a retainer. If the clutch cable breaks when on the road and you have no spare, don't despair. You almost have to be solo when this happens, but I have had a few customers who managed with a passenger. I have ridden motorcycles several times with no clutch. The BMW lends itself to this easily as it has high torque at low rpm. Get the engine running and warmed up. Allow it to idle in neutral, push the bike as fast as you can (I do this while astride) and put it into first. You can be a cowboy and run along side of the bike and jump on as you reach maximum velocity. It will be at about the right rpm for that speed and gets you going in first. Take it up to only about 1200-1400 rpm and preload the shift lever. Let off on the throttle and increase foot pressure on the shift lever. It will pop into neutral if you are gentle. Now as the rpm has dropped to around 1000 or so, shift it into 2nd gear. Going into 3rd is about the same, but there is no defined neutral and it may sort of jerk as it hits 3rd. That is why you must use a low rpm. Stay in the lowest gear that will work for your road speed. Down shifting takes a bit more technique to do it smoothly. You need to try to find the false neutral and increase the rpm a bit before shifting it into the lower gear. I strongly suggest that you learn this technique before you need it. It will give you confidence that you can travel without the clutch. It may also convince you of the need for clutch cable maintenance. I have seen serious long distance riders sort of semi-install the spare clutch cable. It is a good place to store it. a. Protecting the clutch cable On the /2 and /5, the clutch arm has a round spring that is keeping tension to hold the arm rearwards. That spring provides the tension to keep the cable hooked on the arm. If the free play is too great, the spring can fall off and then the cable can drop off of the arm. You are now without a clutch. Keep your clutch cable free play correctly adjusted. Sometimes we used a short piece of thin wire to attach the spring in place. If it falls off, then at least you still have it and can put it back right again. The /2 and /5 have a cotter pin to hold the clutch arm pivot pin in place. This system worked out well. On the /6, BMW changed it and problems occurred. The pin is held in place by a clip. The clip is made of soft stamped sheet metal. It had a way of not getting seated properly and falling off. The pivot pin could then slowly work it's way out and fall off. The clutch arm then fell off too. Sometimes even the three piece throw out bearing would fall out too. More common was for the pin to work its way out of one side. Then the next time the rider pulls the clutch lever, the pin is put in a large bind. The casting that is still holding the pin breaks off. Sometimes both sides will break off. All of these pieces are special and the rider had no clutch. This clip was changed to a normal C clip, but it still needed to be set properly. Check by trying to push and pull the pivot pin out. It should stay exactly in one place. D. Other cables, The speedometer and tachometer cables require occasional lubrication. I like to lube them well and let them drip overnight to drain. With both ends loose one can turn an end by hand and it should be totally free and without any "catches" in it. One symptom is an unstable needle. These cables shouldn't be allowed to have any sharp bends in them. The lower end of the speedometer cable plugs into the transmission at the right rear. It must be covered with a boot in good condition. This cable is famous for directing water into the transmission and rusting the bearings. If you find the level too high and grayish think foamy oil in the transmission, that is an emulsion due to water. Check the speedometer cable boot. Replace with good oil and do it again in 500 miles. Installing the speedo cable must be done carefully. At the upper end, very carefully insert the square end into the speedo. Before fastening with the collar, take a very close look at the place where the outer flange butts up against the speedo housing. There should be no space there. The flared out part of the speedo cable should be flush with the speedo housing. Otherwise you run the risk of putting pressure against the speedo internals and ruining your speedo. When installing a new or rebuilt speedo unit, always replace the cable too. I have "cheated" a few times when the cable is still really good and has no permanent bends in it and all was well. Choke cables on the R75/5 are of two types. These cables have no Teflon liner and need lubrication. The actual choke is really a fuel enrichener. It changed only slightly during the run of the /5 models. The timing retard cable on the R68/R69 needs lubrication. I have no idea if they are now provided with the improved Teflon liners yet. Let me know. The magneto with the timing retard lever has some other issues. |
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This page was last edited:
08/26/2007 - copyright
Duane Ausherman |
