Hello everyone, 

I am the delighted owner of a beautiful K100 RS1 from '91 (0202461) that I bought at ~23.500kms. Since I got it, I rode about 1.500kms in a few weeks on it and recently I've got an issue, the gear selector got stuck and I could upshift till the 4th gear but then couldn't downshift back. The gear selector was actully "hanging" down and not standing inbetween the "up" or "down" position as it should be.

It was on a very hot day (during the heatwave in Europe, about 40°C) and after a few hours I could manage to get bike back in Neutral and ride it home. Since then i've tried the bike again and the gearbox was working properly for the first kms but then was hard to downshift again when the bike got warmer. I did 2 small ride, I didn't wanted to make the issue worse.

In the following link you can find a video of the issue : https://www.youtube.com/watch?v=ThOPHSlZoWo

I've been reading on this forum about it and I am under the impression that it could be an issue with the shaft / clutch spline lubrification and that it'll be nice to do it. Maybe even opening up the gearbox to have a look inside?

Did you already had a similar issue and have some advices for me?
Thank you for your help and time,
Best regards,
Léo !

That looks like a failure of the shift lever shaft's grub screw. You can read about it inside this thread beginning at post #15.

Also shown in this video starting at around 1:06.
https://www.motobrick.com/index.php?topic=4302.0

There are other posts to be found on the site describing this condition.

Thank you very much for your reply, after further inspection it should be that.

I'd like to do it myself with a friend that has some experience with K75 and K100 but he told me that the paralever on the K100 RS1 changes quite a few things, is it harder to remove the rear shaft on those bike? 

Here is a picture of the rear drive.

Laitch wrote:That looks like a failure of the shift lever shaft's grub screw. You can read about it inside this thread beginning at post #15.

Also shown in this video starting at around 1:06.
https://www.motobrick.com/index.php?topic=4302.0

There are other posts to be found on the site describing this condition.

This is where I would start to troubleshoot.  You really don't want that screw to fall out.  I did the grub screw on my K75RT in one long day(about 7 hours start to finish) when I first got the bike.  It's not that hard of a job, just time consuming.  It does give you an excellent opportunity to lube all the splines including the clutch, and make sure everything in the drive train from the clutch back is in proper shape.

It's a few more steps to take off the paralever but still DIY-able.

Be sure to properly phase the drive shaft U-joints when putting things back together:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/dsphase/dsphase.htm

Paralever related

https://www.youtube.com/watch?v=L0_j8SuiFQI

https://www.youtube.com/watch?v=9K1Sm2xfAyw

https://bmwmotorcycletech.info/phasing.htm

Grub screw related

Reply #4 http://www.motobrick.com/index.php?topic=2579.0

http://www.motobrick.com/index.php?topic=9353.0

Part 1 https://www.youtube.com/watch?v=SI6YHhboHJw

Part 2 Inside of the tranny/gearbox and the actual Grub screw shown https://www.youtube.com/watch?v=zVea8TByyT8

Part 3 https://www.youtube.com/watch?v=GOR3Ckfkbsc

Thank you very much for all those links, it is very informative ! I feel like I'll be able to do it myself.

Do you think it'd be possible to fix the grub screw using a flexible extension in order to avoir taking pieces of the transmission out to access it?

Regarding the gearbox, once opened, do I have to change the seals and bearings at showed on this page? Or just the input shaft seal and output shaft seal?

When I did my grub screw, I didn't replace the gearbox seals because they weren't leaking.  Just make sure the shafts are nice and clean all the way down to the seal before you take the gearbox apart, and put a light film of grease on the shaft before you reassemble. 

You can probably get the grub screw back in without taking the guts out, but be prepared to remove the shift drum and the forks.  You will probably have the rollers on the forks fall off and have to move some internal bits to get them and put them back where they belong.  I found that out the hard way. 

A can of brake cleaner spray will do a good job of cleaning the oil out of the hole the grub screw goes into.  After you clean it real good, use a thin wire to put a drop or two of BLUE Loctite in the hole before you put the screw with a little more on it in the hole.  You want to make sure it never loosens up again.

If you have some spline lube, you might want to put a light film on the shift forks where the rollers ride on them and in the grooves of the shift drum.  This will help the shifting along with putting a small amount of molybdenum disulfide powder in the gearbox oil.

Point-Seven-five wrote:When I did my grub screw, I didn't replace the gearbox seals because they weren't leaking.  Just make sure the shafts are nice and clean all the way down to the seal before you take the gearbox apart, and put a light film of grease on the shaft before you reassemble. 

You can probably get the grub screw back in without taking the guts out, but be prepared to remove the shift drum and the forks.  You will probably have the rollers on the forks fall off and have to move some internal bits to get them and put them back where they belong.  I found that out the hard way. 

A can of brake cleaner spray will do a good job of cleaning the oil out of the hole the grub screw goes into.  After you clean it real good, use a thin wire to put a drop or two of BLUE Loctite in the hole before you put the screw with a little more on it in the hole.  You want to make sure it never loosens up again.

If you have some spline lube, you might want to put a light film on the shift forks where the rollers ride on them and in the grooves of the shift drum.  This will help the shifting along with putting a small amount of molybdenum disulfide powder in the gearbox oil.

Thank you very much for those explanation, it will help me a lot !

I've one question regarding the Loctite, is blue the right one to use? On another threat, red one was suggested : http://www.motobrick.com/index.php?topic=9353.0

Kai Ju wrote:To make it easier to start the grub screw, simply move the lever it threads into. This will give you a straight shot at the screw hole.
Make sure everything is grease and oil free, and be sure to apply red Loctite to the screw.

I've looked on the Loctite website and the red one is suggested for warm places, such as the 272 : http://www.farnell.com/datasheets/1920361.pdf

Do you know what's the difference like?

Red Loc-tite 262 is used in permanent applications

Blue Loctite 242 is semi-permanent, easier removal should you have to unscrew in the future

Blue is fine in the gear box.  You will need to go in there with a torch to get the screw out if you ever need to go in there again.

Hot or cold, I never use the red stuff.

Indeed, it might be easier to be able to remove the screw without melting everything down with a torch.

What about the Loctite 243 then? I've read it's an "upgrade" that can withstand some oil : https://www.henkel-adhesives.com/be/en/product/threadlockers/loctite_243.html

"Proven to tolerate minor contamination by industrial oils, e.g. motor oils, corrosion prevention oils and cutting fluids"


I kI know it doesnt change much, but since I am still buying it, might as well go for this one?

I'vI've just removed the gearbox, everything is going fine at the moment, the spline look in great shape and no leaking but the one coming from the "CLUTCH PUSH ROD RUBBER END BOOT".




 

To clean the splines from the lube that's already on it, would you recommend to use break cleaner spray on a microfiber cloth ?

Any degreaser will do. Just make sure the splines are dry before re-lubing.

Point-Seven-five wrote:
If you have some spline lube, you might want to put a light film on the shift forks where the rollers ride on them and in the grooves of the shift drum.  This will help the shifting along with putting a small amount of molybdenum disulfide powder in the gearbox oil.

Things are going well and I'll open the gearbox tomorrow. I've got some Loctite 243, gasket sealant and just bought spline lube, a cartridge of Bardalh BMo2 "Reinforced grease by MoS2 technical agents". Is that good enough ? It is hard to find Moly here in Belgium. It will certainly qualify for the shaft spline lube?

Would this grease qualify to be put as a light film on the shift forks? Or should I rather use some Castrol Molub-Alloy paste White T for the internal parts of the gearbox? I entend to use this one for the input shaft of the gearbox.

I am sorry to ask so many questions, but it's hard to fine precise answers to this kind of questions
I can't wait to get into the gearbox   and fix this screw !

Best regards,
Léo

Ok, it's open and I think that I've found the culprit ! The issue ain't the grub screw, it's the fixation of it ! 

Now I have to find the missing parts inside the gearbox and find how to fix this !

I can't even find the number of this piece  What should I do? Put it back in with some Loctite on it? It seems to fit quite well in the hole it has to be in.

Here is a video of this issue : https://youtu.be/lf2xrtfMjbg

If it were my transmission, I'd tap the hole and use a screw with blue Loctite.  Personally, I wouldn't trust that pin to not work it's way out again.

If you decide to put the pin back in, clean out the hole with brake cleaner, rough up the pin's surface with 100 grit and use that damn red Loctite.  If it holds as well on that pin as it does on brake rotor bolts, you have a pretty good chance that it won't ever work loose again.

Thank you very much for the answer, so there are two options open :

1. Cleaning the hole with break cleaner and then putting the pin back in. I've already tried to put it back in, there is not free play and I was really difficult to put it back out. I had to use a strong pliers. I have been advised to use green Loctite 620, "designed for the bonding of cylindrical fitting parts" and that is oil, shock and vibration resistant. "Typical applications include bearings in auto transmissions."
It can bear temperature up to 120°C with no alteration to it's strenght. This should be the man for the job.

2. Second option is to tap the hole, manually might be better to keep good control of the action and then put a fitting screw with red Loctite 423 for oil tolerance.

I think I'll go with the first one, which means less intrusion in the gearbox and I'll open it again for the next oil change to have a look at the pin, see if it moved. And control as well the "play" in the lever to see if it increase. Then I'd go for the tapping.

I've one more question, the gearbox is made of steel? 

I'll keep you updated on how it went

It took some times but after tapping the hole and putting a screw into it with some Loctite I managed to put the bike back togheter and start it again. It took me several days to assess all the option and get the proper tools. 

For a first try with mechanics I must say that the BMW K100 are pretty easy to understand thanks to all the knowledge shared on the forums, videos and websites ! Thank to all

here is an image with the bolt instead of the missing piece ! This one won't go anywhere anytime soon!

I also managed to get the exhaust welded because one of the collector was cracked, apparently it is quite usual on K100?

Exhaust on the 16v K bikes does indeed crack. Change the rubber mounts to new ones helps a bit too.

leooo wrote:I also managed to get the exhaust welded because one of the collector was cracked, apparently it is quite usual on K100?

92KK 84WW Olaf wrote:Exhaust on the 16v K bikes does indeed crack. Change the rubber mounts to new ones helps a bit too.

It seems that several members with these exhaust systems are successfully using this strategy to prevent cracking of that joint.

In my case it was already cracked....so long term solution came in the form of a nice new Remus...30k miles on it now.