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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Novafrk on September 25, 2014, 03:20:04 PM
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Hey all!
I recently bought an 88 K75s with 48k miles on it. The bike was on consignment at a certified BMW shop. I rode the bike home with no issues, about 75 miles, the clutch was butter. I rode the bike to work the next day about 25 miles at which point I noticed the clutch lever had a ton of free play and was barely disengaging the clutch. I managed to get home, adjusted the clutch per the clymers manual and a couple of youtube videos. (75 mm from the barrel to the cable housing adjusted at the lever, 5 mm free play adjusted with the bolt/locknut on the bell crank at the transmission. Everything seemed good.
Put about 25 miles on it and it was back to tons of free play barely disengaging the clutch. I spoke to a few friends that have owned / own BMW's all said it sounds like a bad clutch cable, and to pack one as a spare. So I replaced the clutch cable adjusted it, and it appears to be doing the same thing with the addition of now as I pull the clutch lever, there is a distinct catch when operated. Like something is just barely interfering but not enough to stop the lever altogether. This started approximately 150 miles after installing the new cable. Two other items of note, the throw out bearing squeals when you engage the clutch (this is where I think my issue lies but was told because it's a dry clutch they make funny noises, keep riding it) and the bolt to adjust the bell crank is almost bottomed out. The bolt being bottomed out makes me think that it may need a clutch or there is something seriously wrong with the throw out bearing/plunger assy.
Has anyone else experienced a similar situation? If so, what was the cure? Thanks for reading.
Eric in Indy
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could #1 be whack... possibly #2... perhaps #4... (http://parts.bmwmotorcyclesofcountryside.com/a/BMW_1988_K75/_51512_5828944/CLUTCH-CONTROL/21_0252.html)
j o
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I too am beginning to think along those lines. The clutch doesn't slip at all, with only 48k miles I wouldn't suspect it. Sadly I have to pull the transmission to remove number one. Oh, well I was gonna do that over the winter to clean and inspect all the splines anyway. Guess I'm just gonna do it a month or so early.
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Hmm, if no.4 was wack That would be an easy quick fix... nah, not with my luck. :nono
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To me it sounds like the problem could be the bearing and/or the push piston, anyway easy to check.
Take care when opening the boot clamp and releasing the lever arm, the spring inside is rather long.
BTW. The free play at the hand lever is 2 mm on a K75.
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No warranty I guess...I'd be thinking along the lines of -- what could the PO have patched up so that it would appear to be fine for 200 miles before failing? Used car dealers are masters at the art of masking problems just well enough to get the thing out the door...but then again I guess I'm just not a very trusting person :-)
My clutches haven't ever made any funny noises. That sounds pretty bogus to me.
I have heard of people having problems if the cable isn't routed properly through the frame. It has to navigate between some innards...did the cable you replaced look worn or new? Maybe PO replaced it improperly and then when it started acting up just decided to jettison the bike. If it was routed wrong and you replicated that then it's still routed wrong and you'll have issues until it gets corrected.
Maybe someone else can explain better how an improperly routed cable can affect clutch operation...I don't know details, just that my K bike guru buddy mike told me to make sure to get it right by taping the front and rear ends of the old and new cable together and fishing it thru the same way. He told me what could happen if it is misrouted but it was a long time ago and I forget xactly what he said.
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Thanks for the advice. I believe the cable is routed correctly. The cable I removed didn't look new. There was wear on the barrel ends and the rubber boot was showing signs of breaking down. I taped the two cables together and pulled it up from the bottom. The old cable went up across the engine under the frame rails, and was strapped in place with factory looking plastic hold downs.
It was purchased as is. The shop I got it from has a spotless reputation and has been in business for 64 years. I'm sure if it was something they had seen they would have fixed it. That said, I tend to be overly trusting. lol.
I plan on looking into it this weekend. It needs tires and the expansion tank started leaking, so I might as well pull the transmission and inspect the input splines. That way I'll know what I've got there and won't have to redo if for a while. Thanks for the input and I'll let you all know what I find out.
Cheers!
Eric
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have you checked the clutch lever (under the tranny)? if you can remove slack by adjusting cable and then slack returns after use perhaps the lever is cracked/bent/otherwise damaged enough so that it distorts after repeated use.
stranger things have happened......
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I haven't looked closely at it. But that was also in the back of my mind as something to look at.
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all bmw dealers are certified... certified whack... where did you getts this 750 motobrick...
j o
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I got it from Moody Cycle in Kokomo. It was on consignment.
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Does the sidestand retract when you pull in the clutch lever?
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Yep, sure does.
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I figured as much but the self-retractor mechanism is the first linkage point between the clutch hand lever and the clutch control lever so it's worth looking at.
So while this excessive freeplay thing is happening, if you slip a long screwdriver under the clutch control lever and push it up away from the cable ball end, i.e. release the cable end and disengage the clutch manually bypassing the hand lever, is there no resistance or a lot? The clutch control lever takes a good amount of leverage to push the clutch pushrod forward and the resistance should start as soon as end of the adjustment screw hits the piston that rests against the pushrod. If that rubber boot compresses without significant resistance, I'd think the problem lies behind the boot. If you have lots of resistance then maybe the problem lies forward of that point with the cable linkage.
At least that's what I'd be thinking with my scant knowledge...then I'd float that theory here and hope someone corrects me, which most of the time they do.
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I think you have a bad Piston/Bearing (#2, #3).
Easy but pricey to replace. Free and quick to take it out and check it.
Pull the clutch in with the hand lever, then stick a wooden wedge or something between the muffler and the clutch lever (#7) so that the lever stays in while you remove the clamp (#5). Remove the wedge / release the clutch then remove the fragile boot (#6) then #2, #3 and #4).
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you may wanna have a new boot in hand when you give this a go... they are old and known to fail when man handled...
and never let anybody butts you pull in that clutch lever... it will haunt you forever...
j o
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BTW the piston bearing on my 95 k75 is different than the one depicted in the diagram. The 95 has a one-piece piston and bearing. My 94 k75 has the two-piece one as depicted. The 95 had a clutch job on the early 2000s so it's possible the part was redesigned at some point and the dealer replaced the old bearing/piston with the updated part when the clutch was done.
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Sounds like clutch pushrod is beginning to go through the spring plate
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The piston/bearings on my '91 is a one-piece part too.
BTW - I completely removed the side-stand retracting mechanism from the clutch controls. Was worried about it stressing the clutch cable if mishandled or mis-adjusted. One day I will take a left turn with my sidestand down and regret it.
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I have decided to stop riding it for now. I will tear into her this week. Max's BMW sells the one piece part, but cautions you have to remove the bushing from the rod or use the different style rod. I'll yank the transmission and clean and inspect everything, input splines etc. I'll let you guys know what I find out. Thanks for all the brain storming.
Eric
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Sounds like clutch pushrod is beginning to go through the spring plate
Interesting -- in the pic at the linked page below there's a bearing at the center of the spring plate...has anyone known that to fail or detach from the spring plate?
http://www.bmw2valve.com/motorcycle/2121784.html (http://www.bmw2valve.com/motorcycle/2121784.html)
And if it does, what happens to the end of the pushrod once it's past that bearing? Will it get chewed up?
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Iirc it is a bushing. From the description something is getting "longer" it is either on the back side of the pushrod or the front. If everything is ok in the back that would be my guess. I am more familiar with the r setup but I have been inside of the k housing and it is the same setup. Maybe soe of the more seasoned k heads can provide additional guidance.
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Normally the end of the clutch push rod rides in a brass bush in the end of the engine output shaft. It is supposed to stick through it.
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Hello all,
I'll be tearing the bike apart this weekend. Any tips / hints to make things easier? Anything else to look out for while I'm in the patient?
Thanks in advance!
Eric
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Lots of things -- but most of them have already been discussed in detail on this forum. Search 'spline lube' and you'll get everything you need, but here are some quick tips --
Guide bolts help pull the trans off straight out. You need to make sure it doesn't drop down when you get it disengaged or else you could damage the clutch pushrod.
Centering tool helps reinstall the clutch -- but it's not a necessity. Read up on that and know what what to expect when you get to that point.
Some people swear by a sturdy sawhorse to keep the rear end off the ground and stable. If you don't have a moto platform lift you can read up on how other folks here do it.
Replace the 6 clutch bolts and washers with new ones...they are a single use item.
That's what I come up with off the top of my head...but you're best off searching the forum.
Good luck...you'll have fun. The folks here have nothing better to do than check the forum for new posts often so if you have any questions someone's likely to answer within a couple hours.
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Thanks for the response! I wasn't aware that the clutch bolts were a one time use. Are you talking about the ones that hold the pressure plate to the flywheel? I haven't gone over the clutch R&R proceedure yet in the manual. Maybe it mentions it there. Everything else you mentioned I have read about. Thanks again!
Cheers!
Eric
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Yes, those are the bolts. It's highly recommended to replace the clutch bolts -- lots of comments about that on the forum here -- and torque them properly. I've had to drill them out -- no big deal -- but why complicate things when torque wrenches are dirt cheap.
The manual is the manual -- lots more info here. Btw I got one of those plastic parts organizers from HF and slapped some labels on the dividers to help keep track of bolts and various bits. Very handy -- most everything is 5, 6 or 8mm of varying lengths depending on which side of the bike and the purpose of the bolt, so it's important to keep track and label everything the first time.
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One more tip to add if you end up pulling clutch housing, discs and spring- be sure to mark the components so they stay aligned in the same way the were removed. These thinks are factory balanced by drilling metal off here and there, and can be tricky to figure out if you lose track. The factory did put some paint to mark them, but mine was pretty much undecipherable. Also be careful if you use a puller on the clutch housing, as I accidentally pushed the brass bushing that accepts the end of the push rod way back into the output shaft (then had to extract with bolt and slide hammer, and of course replace).
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Could also be a idea to change the o-ring behind the big nut in the clutch basket....as this dries out and cracks.
The nut is also one time use.
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These are all great ideas. Thanks guys.
I'm a big fan of taking a picture, bagging and tagging parts as I pull them off the bike so there is no question of where they go. Too many painful lessons learned on my Triumph. :yes
I assume the Oring is holding back fluids of some sort? I'll have to read up on that too. Thanks again guys.
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There is supposed to be ball bearing in here somewhere right? :falldown:
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Splines on the FDU looked really good. So I'm happy about that.
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It was something like this I suspected....ref. reply #4....looks like someone have forgotten to mount the
ballcage which also include the balls.
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I agree with you Inge K. Here is a picture of everything I took out of the clutch. I don't see the bushing that is supposed to go on the end of the push rod either. Clutch miked out at 5.35 mm. avg. The fly wheel and pressure plate surfaces looked good too. I'm planning on switching to the sealed throw out bearing that uses the different designed push rod.
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I don't see the bushing that is supposed to go on the end of the push rod either.
If you look into the center of the intermediate shaft you should see it.
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Parts have arrived. Just waiting on moly paste to put the bike back together. Hopefully by the end of the week.
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Hey all,
The bike is back together with the exception of the Wheels and brakes. All 3 sets of pads were worn out. I should be riding it again by Thursday. I have fired up the bike and everything seems happy. The clutch adjusted out nicely to about the middle of the bolt.
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The bike is all road worthy once again. Everything seems happy and I am pleased. Now to get the right half of the gauge cluster to work. Off to the search results.
A quick thanks for the suggestions, I followed them all. The oring was very hard and brittle, so I'm glad I changed it. New bolts, and what not too.
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Great to hear! Don't forget to post the pic of where you are when the bike turns 100,000 on the Six Figure Club page...
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I've only got 51,xxx miles to go! I should hit that in about... 5-7 years!
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If you do it in two maybe Johnny will send you a t-shirt.
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If there's a t-shirt involved, challenge accepted!
:riding: