Hi Friends!
   I have a couple issues on an otherwise perfectly running 1985 K100rs:

   Issue 1) The idle fluctuates. The bike mostly idles smoothly at about 975rpm. Every few seconds, though, it will briefly drop lower. It'll drop to 900-925ish for less than a second and then come right back up. It's perfectly smooth while the throttle is on. The problem is at idle only. And while it's at 975, it's very smooth.
   The most recent thing I did to the engine was balancing the throttle bodies. Honestly, I don't know if it was doing this before the throttle body job. As the bike gets better and better, I find that I'm focusing on smaller and smaller problems. So, maybe it's always done this and I just never noticed until now. Any thoughts?

   Issue 2) Intermittent transmission trouble. Sometimes, when I try to downshift the shift lever won't move at all. If I let the clutch out, then pull it back in and try again, then the transmission usually works perfectly again.
    This happens only after the transmission is fully up to temperature. Never in the first half hour of a ride. It's downshifts only. I haven't had a single missed upshift. The problem seems to be worse when I'm going downhill, though I'm not sure about that. It's intermittent enough that it's hard to pin down what makes it better or worse.
   I changed the transmission oil 1500 miles ago and put in Castrol Syntrax Limited-Slip 75W-90. The transmission doesn't leak and the oil still looks like new. No darkening, no metal dust. I tried adding a little bit more oil. I took the oil level up from just below the line on the dipstick tool to just a touch above the line. That helped, actually. The problem doesn't happen as often now, but it still happens.
   Hopefully this is an easy fix, rather than the beginning of the end of my transmission. What do you think?

   Many thanks as always!
   -Jon

Hi Jon,
I've no ideas about the idle fluctuations.  However, I suspect the difficulty you sometimes have with shifting my be a clutch issue rather than a transmission problem.  When was the last spline service performed?  Do you know?

I greased the clutch splines in May. About 3000 miles on the bike since then. The clutch action at the lever is perfectly smooth. When the transmission lever is stuck I can rev the throttle with no effect at the wheel, so I don't think the clutch is sticking or dragging. Could there still be something amiss with the clutch that I'm missing?

Did you adjust valve clearance before you balanced the throttle bodies?
Are all vacuum takeoff caps and the pressure regulator hose secure and in good condition?
Is the air cleaner in good condition?
Are all the rubber parts attached to the air box in good shape?
Have the rubber throttle body tubes ("bushings" in the BMW fiche) been checked for leakage?

What is the measurement of handlebar clutch lever free play?
What is the length of exposed cable measured between the cable housing and the clutch release arm?

Laitch wrote:Did you adjust valve clearance before you balanced the throttle bodies?

Checked all valve clearances a few months ago. All were perfect.

Laitch wrote:Are all vacuum takeoff caps and the pressure regulator hose secure and in good condition?

Yep.

Laitch wrote:Is the air cleaner in good condition?

Yep. Fresh air filter.

Laitch wrote:Are all the rubber parts attached to the air box in good shape?

Yep. Also checked the MAF Sensor when I changed the air filter.

Laitch wrote:Have the rubber throttle body tubes ("bushings" in the BMW fiche) been checked for leakage?

Yep. I did that as a first step to adjusting the throttle bodies. No leakage at all.

    I know the throttle body adjustment is suspect, since that was the last thing I did. But wouldn't maladjusted throttle bodies manifest as a consistent rough idle? The 3-4 seconds of idling perfectly between each dip in RPM leads me to suspect a cause that's acting on all cylinders simultaneously.

Laitch wrote:What is the measurement of handlebar clutch lever free play?
What is the length of exposed cable measured between the cable housing and the clutch release arm?

These I haven't checked (and the bike is at home so I can't check right now). The clutch doesn't slip when the lever is out and it doesn't drag when the lever is in. What more can you ask of a clutch? With the bike off, on its center stand, in gear, clutch lever pulled in, I can spin the rear wheel by hand as freely as if the bike were in neutral. Isn't that a pretty solid indication that it's releasing as it should?
   -Jon

Bikesmith wrote: What more can you ask of a clutch?

It can be asked to help you downshift easily as it was designed to do.

Those measurements will indicate if the clutch is correctly adjusted, all other conditions being OK. Those measurements are part of a clutch adjustment and although perhaps not as memorable as a first kiss, they should be kept in mind because as a clutch wears they need to be checked and reset if necessary.

What I recall about getting to terms with the gearbox was that it loved to be on the throttle when downshifting, just a short blip as you go for the clutch to release the pressure on the gearbox and I found no further issue with the gearbox. Just a little foible with these girls at a guess.

K75cster,
   I can accept foibles on my Enfield, but since my brick is 45 years newer, I hold it to somewhat higher standards. I don't think perfection is too much to ask for .
   I took the bike out again yesterday after checking to make sure the clutch was properly adjusted. Once I let go of my preconceived notion that the clutch was not to blame, I realized that Brickrider and Laitch were right. This is clearly a clutch problem. Trying to downshift without touching the clutch lever gives exactly the same symptom: The shift lever doesn't move at all. Also, when the problem happened I tried blipping the throttle while holding the clutch in. Problem gone.
   So my clutch rebuild parts (Clutch boot, housing cover bolts, etc.) are on the way. I've been meaning to rebuild my center stand anyway. This is my opportunity. Plus, it's snowing. I'm not riding for a while anyway, so I might as well dive in.
   I've been reading the Clymer book in preparation and rewatching Chris Harris' spline lube video. I have just a couple of questions for the clutch experts here. First, based on my symptoms, is there any specific problem I should be looking for? Should I pull out the clutch housing, or just the rest of the clutch? If I do pull out the clutch housing, should I grease the splines of the engine output shaft? Clymer doesn't mention doing so, but it seems to me like a good idea.
   -Jon

Two things I have found to improve shifter action:

First, lubing the output shaft splines makes a big difference in clutch action and ease of downshifting.  I'm not positive, but it looks to me from personal experience like these splines were not lubricated from the factory.

Second, I added about three heaping tablespoons of 1.5 micron powdered Molybdenum disulphite to the transmission oil.  After a couple hundred miles of running the moly coats the internals and shifting is way easier and smoother.

When riding, I have found that pulling the clutch in more than about half an inch actually makes shifting harder, especially on downshifts.

Bikesmith wrote:I took the bike out again yesterday after checking to make sure the clutch was properly adjusted. 

How did you determine it was "properly adjusted?"

Issue 1) The idle fluctuates. The bike mostly idles smoothly at about 975rpm. Every few seconds, though, it will briefly drop lower. It'll drop to 900-925ish for less than a second and then come right back up. It's perfectly smooth while the throttle is on. The problem is at idle only. And while it's at 975, it's very smooth.
   The most recent thing I did to the engine was balancing the throttle bodies. Honestly, I don't know if it was doing this before the throttle body job. As the bike gets better and better, I find that I'm focusing on smaller and smaller problems. So, maybe it's always done this and I just never noticed until now. Any thoughts?


Hi, I am not shure about idle fluctuations but did you clean injectors? Maybe to try with some injectors cleaner or clean by profesional?
One faulty injector could inject more fuel than needed and RPM drop for second?
Just thought.
Regards

You write that you lubed the clutch splines in May. What was your guide to clutch spline maintenance? When the drive line is apart all splines should be lubricated. So did you not clean and lubricate the transmission output, drive shaft, and final drive splines? Harris covers all that in his video.

You haven't indicated that the clutch is slipping, which would be a sign of a worn or contaminated clutch. You haven't indicated that oil is dripping from the weep hole below the clutch/transmission assembly—a sign of possible clutch disc contamination. It seems to me your clutch assembly might be ok.

You've ordered a "clutch boot, housing cover bolts, etc." Does the etc. include a new spring for the boot, a new clutch pack, a new clutch nut, o-ring and main seal?

I'm still uncertain if you've got the cable adjusted correctly which was my question when I read your first post, because you wrote that you had already lubed the input spline shaft. If what you have written so far is accurate then the problem might be transmission centered. Adding moly as recommended, and blipping through the downshifts could be the remedy, or the problem may be more complicated and internal.

When I first got my bike, I had to blip the throttle to downshift. Double-clutching—as you have written you need to do—was unnecessary. After reading enough confirmation that stubborn downshifting could be due to dry input splines, I lubed them. I now can pull in the clutch and downshift—with or without blips, depending on the audience—at a standstill, or rolling, smoothly through all the gears. Occasionally, first gear might take double-clutching at a standstill, but not often. I pull the lever fully—no problem.

My bike only has 59K on it so that may be an advantage.

Bikesmith wrote:These I haven't checked (and the bike is at home so I can't check right now). The clutch doesn't slip when the lever is out and it doesn't drag when the lever is in. What more can you ask of a clutch? With the bike off, on its center stand, in gear, clutch lever pulled in, I can spin the rear wheel by hand as freely as if the bike were in neutral. Isn't that a pretty solid indication that it's releasing as it should?

I wouldn't say "solid" but a possible conclusion however the cable length adjustment is very important as it will put the whole mechanisim into the correct position so as to get the required and full movement of the clutch pushrod. The clutch adjustment with locking nut ensures the actuating arm is in the correct position to the pushrod end, and the clutch lever free-play adjustment ensures the cable is released enough to back-off the actuating arm from the pushrod end sufficiently to ensure there's no pressure on the pushrod when the clutch lever is released.
How the clutch may or may not be working while its on your centre stand will be a different thing to how it works on the open road as there are far greater forces acting on the whole drive train when you are downshifting as you scream into a corner at 100kph or even just cruising up to a set of lights.

I have this same problem with my naked '89 K100 (166k). Clutch adjustment is always correct. Greasing the clutch splines has not helped. Adding moly to the GB, while I thought it was shifting a little smoother overall, the problem shifting down to 3rd or 2nd remained the same. The only thing that helped is to ensure you get a good blip and be very positive with the gear-lever movement. As it's got worse I've found that its difficult to get it back into gear while moving and so have needed to pull over to get it down to 1st and start again.

My conclusion is that something like one or more of the GB fork selectors are worn/bent/damaged although I've not found any unusual metal swarf in the oil. I have a recon'd GB to go in next year when I get around to doing a little restoration on her.

I've not had the clutch out of my old girl so I'm not discounting any problems there. I may find that the pressure plate is kaput.

Laitch wrote:

Bikesmith wrote:I took the bike out again yesterday after checking to make sure the clutch was properly adjusted.

How did you determine it was "properly adjusted?"

Indeed. The only way to determine if a clutch is adjusted properly is to... adjust it properly!!

1. Set bottom cable length to 75mm
   
2. Finger tight clutch adjuster bolt and lock it off
   
3. Adjust for 4mm free play at the lever
   

As for the irregular miss. Sounds like something amiss with the HT. Start with SPs, HT leads and connectors (check for corrosion). Plenty of info here on the forum for testing all that or just ask. You are seeing it happen at idle only because its just not noticeable at higher rpm. I've experienced that same miss at low rpm a few times and a new set of SPs has been the solution for me.

Holister,
   Thanks for the reply. This one's mysterious. When this first started happening, I was suspecting GB forks as well. I'm now leaning more toward clutch, since the symptom  is exactly the same as trying to shift without pulling the clutch lever and if I blip the throttle after pulling the clutch lever but before trying to shift, then it works perfectly every time. I don't know. I could be wrong, of course. We also could have similar symptoms from different problems.
   I think I'm going to rebuild the clutch regardless. It might help, might not. But I have yet to see the clutch. I'd like to actually put eyes to the thing to know it's good, rather than relying on the the word of the PO. Any thoughts on whether I should pull the clutch housing or just go as far as the pack? If I do pull the housing, what are your thoughts on greasing the engine output splines? The Clymer book doesn't say to, but it seems to me like a good idea.
  I'm also going to replace the clutch cable. It's within the range where it can be adjusted properly (Using the technique you described), but I have to back the adjuster at the lever pretty far out. Couldn't hurt to replace that too, right?
   As for the idle miss, HT leads is a good idea. I just put the plugs in a month ago, but I didn't replace the leads then. Probably should have.
   -Jon

If the clutch splines or the input shaft splines are worn it will cause downshift problems even if you have a ton of grease on them.
The irregular idle could quite possibly be a badly adjusted air bypass setting in the MAF sensor unit.
When setting the idle you need to open the bypass screw in the MAF then set the 4 air bypass screws in the throttle bodies then once they are set screw the MAF sensor screw in till the engine changes tone or falters the back it out till all is sweet then 1/8 to 1/4 turn (take your time doing this as the engine can take a few seconds to respond to the minute changes in air). This ensures the flap opens as soon as the throttle is opened. If the setting screw is in too far and not enough air gets through for idle the flap will open and close a tiny bit giving a faltering idle.  This is from my experience on the EFI Kawasakis but should apply equally to the Ks as they both used the L Jetronic system, the Kawasaki only for a few years.

Bikesmith wrote:.....
Any thoughts on whether I should pull the clutch housing or just go as far as the pack? If I do pull the housing, what are your thoughts on greasing the engine output splines? The Clymer book doesn't say to, but it seems to me like a good idea.
 

Removing the GB will expose the clutch. Remove the o-ring to take the clutch out. Careful how you pull the GB back and get it clear as you can easily damage the clutch pushrod. You'll have to replace the o-ring and should also do the main seal while you're in there.... and of course clean and re-grease the splines. I think Rick's advice on worn clutch/input spline is probably spot on.

.....
 I'm also going to replace the clutch cable. It's within the range where it can be adjusted properly (Using the technique you described), but I have to back the adjuster at the lever pretty far out. Couldn't hurt to replace that too, right?

I'll take a punt and say your clutch pressure plate may be kaput. Anyone else like to comment?
The cable would have to be very old to be stretched that much. It should only really need replacing when the liner wears out and it starts to bind or the cable stresses at the top due to no lube in the roller in the lever.

Bikesmith wrote: If I do pull the housing, what are your thoughts on greasing the engine output splines?

In post #3 of this thread, Jon, you wrote that you lubed the "clutch splines" in May. In this post you are referring to engine "output splines". Where is the location of the "clutch splines" that you lubed in May?

Rick,
   I can definitely see how the splines being worn would cause this issue, but would it come on suddenly? I did two 1000 mile trips this summer, plus another 1000 miles locally, with no transmission troubles whatsoever. It's only in the last 150 miles that this issue has begun.
  Adjusting the MAF is a good idea. Even if that isn't the source of the issue, it couldn't hurt to make sure that adjustment is perfect. Thanks!

Holister,
   So, you do think I should pull the clutch housing? And you do think I should grease the engine output splines? Any idea why the Clymer manual and the BMW service manual both say not to? Replacing the main seal while I'm in there is an interesting idea. Should I do that preemptively even though last time I had the transmission out I saw no sign that the seal was leaking?
   I agree that replacing the clutch cable seems like a long shot to help, but I currently have an old cable on the bike and a new one in my tool box. Might as well switch them, right?

Laitch,
   Between engine and rear wheel there are four splines:
      Interface of drive shaft to final drive: Greased!
      Interface of transmission output to drive shaft: Greased!
      Interface of clutch plate to transmission input: Greased! This is the one the Harris video details.
      Interface of engine output to clutch housing: This is the one I haven't seen yet, since I didn't pull the clutch out when I removed the transmission in May. Even pulling the clutch pack won't get you to this spline. You have to pull the clutch housing to get to it. This is the one I'm really curious about since both Clymer and the BMW service manual don't say to grease it. Why not? Is it because the splines don't slide past each other in this one the way they do in the others?

   -Jon

Bikesmith wrote: This is the one I'm really curious about since both Clymer and the BMW service manual don't say to grease it. Why not? Is it because the splines don't slide past each other in this one the way they do in the others?

I'm never quite certain if I understand what you are trying to convey, Jon, but in this case I think the answer to your question is because those parts are lubricated by engine oil.

Oh! OH! Thank you, Laitch! That's the missing piece I hadn't gotten. I'd been thinking that the rear main seal was contacting the engine case on the outside (correct) and the engine output shaft on its inside (wrong) . I finally just Googled up a bunch of pictures of how that all fits together. The inside of the main seal is riding on the clutch housing itself. Everyone can disregard my question about greasing that spline.
   I also now better understand Holister's suggestion to replace the main seal. Once the clutch housing is out, the main seal is just sitting right there, completely exposed. I might as well change it. Increased trustworthiness for an extra $40? Yes, please.

Bikesmith wrote:Oh! OH! Thank you, Laitch! 
Increased trustworthiness for an extra $40? Yes, please.

Consider not getting so excited by one random comment on a website, Jon, until you get some corroborating input from other sources.

Were you using Harris's video for instruction when you were doing input spline lube, Jon, but decided not to inspect the friction disc and other components? In that video he also explains clutch cable adjustment procedure and adjustment values, too. 

What is the name of the product you used to lubricated the input shaft splines? Did you clean the splines? Did you look at their profiles to judge their wear? Did you have a reference photo of splines in acceptable condition for comparison? If you did, where did you get it?

If you weren't using that video and didn't have a manual, how were you guided through all the procedures? If you did, why couldn't you give us the handlebar clutch lever free play measurement when asked? These values tell prospective respondents more than terms like "properly adjusted" or "adjusted according to the manual".

Is your clutch release arm adjusting nut backed all the way out, turned all the way in, or is it somewhere in between?

If you're riding that bike at 50mph and suddenly twist the throttle wide open, does the clutch slip? Have you tried that?

Hollister's suggestion of a failing pressure plate is compelling. I had one lose spring tension on a VW bus once. It affected both shifting and acceleration. 

I'm not convinced that replacing the clutch pack is worthwhile yet unless you have money and time that you just can't spend doing something else. It does keep the spare parts industry healthy though, and we all want that.

Laitch wrote:

Bikesmith wrote:Oh! OH! Thank you, Laitch! 
Increased trustworthiness for an extra $40? Yes, please.

Consider not getting so excited by one random comment on a website, Jon, until you get some corroborating input from other sources.

    Those two lines are from different parts of my post. In the first line, I was excited because you had disabused me of an incorrect assumption. Once I realized the actual location of the rear main seal, what I had been wondering about became clear. Thus my excitement. And gratitude.
    In the second line, I meant that for $40 I can have the trustworthiness of a known new rear seal instead of one of unknown age and condition. Seems prudent to me.

Were you using Harris's video for instruction when you were doing input spline lube, Jon, but decided not to inspect the friction disc and other components? In that video he also explains clutch cable adjustment procedure and adjustment values, too.

I was using Harris' video, and the Clymer manual, and the BMW service manual. Yes, I decided not to open up the clutch at that time. I may have been a bit impatient to ride the bike for the first time. In retrospect, checking the condition of the clutch would have been wise. That's why I'm doing it now. I also now have a much lower opinion of the previous owner's mechanical ability than I did at that time. Makes me less likely to assume something is good, more likely to check for myself.

What is the name of the product you used to lubricated the input shaft splines? Did you clean the splines? Did you look at their profiles to judge their wear? Did you have a reference photo of splines in acceptable condition for comparison? If you did, where did you get it?

  I used Staburags NBU 30 PTM. Yes, of course I cleaned the splines. Yes, I checked the wear.

If you weren't using that video and didn't have a manual, how were you guided through all the procedures? If you did, why couldn't you give us the handlebar clutch lever free play measurement when asked? These values tell prospective respondents more than terms like "properly adjusted" or "adjusted according to the manual".

Is your clutch release arm adjusting nut backed all the way out, turned all the way in, or is it somewhere in between?

  I could have said that there was 75mm of exposed cable at the transmission, an adjuster bolt right about in the middle of its range, and 4.2mm of free travel at the lever. I didn't say those things because I wasn't unsure about it being correct. I figured the conversation would be more helpful if it focused on things that are unfamiliar to me.

If you're riding that bike at 50mph and suddenly twist the throttle wide open, does the clutch slip? Have you tried that?

   Of course I've done that. I do that all the time. Doesn't everyone? It's really fun! No, the clutch doesn't slip.

Laitch wrote:Hollister's suggestion of a failing pressure plate is compelling. I had one lose spring tension on a VW bus once. It affected both shifting and acceleration.

   I agree. That's why my plan is to open the thing up and see what it looks like inside.

I'm not convinced that replacing the clutch pack is worthwhile yet unless you have money and time that you just can't spend doing something else. It does keep the spare parts industry healthy though, and we all want that.

   I didn't say I intend to replace the clutch pack. I said I'm going to open it up, inspect it, replace any parts that are faulty or (like the rear seal) cheap enough that I'll do it for peace of mind. Hopefully the clutch pack is good. If not, I'll repair or replace whatever is bad.

Bon Voyage then!

Bikesmith wrote:Rick,
   I can definitely see how the splines being worn would cause this issue, but would it come on suddenly? I did two 1000 mile trips this summer, plus another 1000 miles locally, with no transmission troubles whatsoever. It's only in the last 150 miles that this issue has begun.

These things do tend to sneak up on you. Bit like needing reading glasses
I do think that the only way you will get to the bottom of this is to remove the transmission and inspect the clutch components.

Update: All problems solved!

   I pulled the whole driveline apart. As Rick said, it was the only way to definitively diagnose the situation. The problem was the splines on the transmission input shaft. The shaft had a bit of a twist to it. I reckon that between increasing twist of the shaft and normal wear of the clutch friction plate allowing it to engage the transmission input just a little further, it finally reached the point where the binding of the splines was just enough to keep the clutch from disengaging properly. I also found that the previous owner had installed the clutch without a thrust washer, so the clutch to transmission splines weren't engaging as fully as they should have. I don't know for sure if that exacerbated the twisting of the shaft, but it certainly didn't help.
   I looked into replacing the transmission input shaft, but I actually couldn't find one. Plus, my transmission was leaking at the output shaft as well, so I just bought a whole replacement transmission that I found dirt cheap on eBay.
   So now the bike is back together with:

• New rear main seal (Old one was leaking a little)
  
• New clutch pushrod pilot bushing (Old one was slightly deformed)
  
• New clutch nut, bolts, o-ring
  
• Replacement transmission (Better than my old in every way. Clearly much lower mileage)
  
• New center stand bushings (It was getting pretty wiggly)
  
• New clutch pushrod boot.
  
• New spark plug wires (Cleared up my idle issue)
  

  The clutch was in perfect condition. Tons of life left in the friction plate. No oil or grease in the clutch even though the rear main seal was leaking. It had just started leaking. When I pulled the transmission six months ago there was no sign of a leak. So I just cleaned and greased the clutch and put it back together.
   I took the bike out for a test ride this morning and it was perfect. It was also incredibly cold. December in Colorado is not ideal for motorcycling. That's okay, when the weather warms up, the bike is ready!

That's good news.  Sounds like you're removing many years of wear and tear. 

Knowing Colorado weather, you shouldn't have to wait too long to be back out there again.