Hi all

I recently bought an 88 K100 with 85k on the clock and no mot (been off the road for the past 6 months). The obvious issues are two oil leaks and the starter not ticking over all the time (common sprag clutch issue it seems). 

Over the last week I've done loads of reading and non stop vids on these issues. I ordered a new main oil seal and relevant bolts etc to put the bike back together. Over the past two days I've been stripping the bike down. 

Chris Harris videos on YouTube have been really useful for the strip down so far. The Haynes manual seems to miss most of the detail...
The rear splines and drive shaft look in excellent condition. Very well defined teeth and no burring or shredding, really chuffed given the price I paid for the bike. 

I've taken out the 6 gearbox housing bolts as I'm attempting to get to the main rear oil seal. I removed the two bolts holding on the gearbox housing to the rear frame, however the housing wouldn't shift. Even with a jack bracing it there was no movement. Am I missing something here? Possibly the removal of another bolt? Or is it possible the housing is just being stubborn? As mentioned I've removed 6 housing bolts and two that mount to the frame. The starter and all other items have been detached from the housing. 


My plan was to take out the gearbox, clean and lube the splines, then remove the clutch and then change the rear main seal... I'm expecting it to be a bit messy. 

Where does the sprag clutch fit into this? I can't picture where it's positioned. I found the following link however not sure exavtly where the sprag is being pulled from with the bearing puller. Might be easier once I have the gearbox out! https://www.k100-forum.com/t4116-sprag-clutch-cleaning-the-sprag-clutch-and-bearing-replacement 


Thanks
Mike

Welcome to the forum!

As for the gearbox... I assume the frame is off, so take a soft mallet to it. Chances are that it's corroded to the bell housing. Once the clutch is off off, you're going to hit a piece of BMW stupidity. They used No. 30 torx bolts to hold the bell housing on. You'll need to get down with a torch and make sure you've got all of them (eight, I think). One or two are partially hidden. Don't mess with them - go straight in with the impact driver because they will be stuck. Also, make sure you have a sacrificial Allen driver (6mm, IIRC) because it's almost a given that one or more of the torx bolts will round off. Replace them with bog-standard Allen bolts.

Alby is using the bearing puller to drag the alternator drive drive off. Look at the front of your alternator: that's where the vanes fit. Truthfully, I must have got lucky because I was able to pull the alternator drive off by hand on the two Ks that I've done. The sprag clutch is the other side of the housing.

How to get a stubborn transmission to move back using block of wood and hammer: Do this on both sides:




There are 17 Torx bolts holding the bellhousing on. If you are careful and use a good Torx bit you can get them all off without stripping their heads. You may want to apply some antiseize when putting them back in.



If you do strip any Torx heads then just drill the heads off to remove them. They are fairly soft and easy to drill. Once you get the bellhousing off the remaining studs will be easy to remove as long as you didn't go overboard drilling the heads off.

Thanks guys, really useful insight. The pics help!

Yes I did have all bolts included the two mounting the gearbox to the frame off but it was stuck. I'll try the rubber mallet and piece of wood combo next! Is there any sort of seal around the housing marrrying them together? 

Once the gearbox housing is off I'll clean and lube the splines and am I right I thinking the clutch will then be on display and the umpteen bolts you speak off need to then be taken off to get to the bell housing off to access the alternator drive? 

I think (well hoping) that the main rear seal is between the clutch and bellhousing, meaning that I can change this seal without the bellhousing coming off? I'm a bit anxious now incase a bolt of two snaps or sheers.

Thanks guys

No seal or sealant between the trans and BH.

BH doesn't need to come off to deal with clutch or rear seal.

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/clutchnospecial/clutchnospecial.htm

But if you are in that far........go and do the sprag clutch, take it out and clean it

Another one of those 'If you are in that far' ............

Replace the O ring under the clutch nut, as over time they become brittle and leak.


Mike

Cheers guys. I have a new locking nut and also the washer To go with it, the only thing I don't have are replacement bolts incase any in the housing sheer off. Unfortunately I won't be able to do this now until Friday so will try to source some bolts for a worst case scenario. 

So far I'm supposed at how straight forward this bike has been to work on. My first motorcycle although have experience with cars. It's nice being able to reach everything relatively easily!

There is a oil leak towards the front of the engine block which I think is oil pump related. Will look into that but any thoughts confirming this would be appreciated

Most likely oil pump but just check the sump bolts are correctly tightened. I found a small leak recently and one of them was a little loose, no idea how or why. Tightened it back up and checked the rest and it stopped.

However its more likely the oil pump.

If you do take the sprag clutch apart, be careful not to dislodge any of the little toggles. They have little tiny springs holding them in and are fiddly to reassemble.

Thanks again chaps. What should I use for cleaning the sprag? 

Also does anyone know the length of the clutch housing bolts? They have them on motorworks but at almost £2 each and postage on top it seems a bit much for some bolts. 

Great source of help on here so far. Awesome

M6x25

Acetone soaking for sprag clutch......

Thanks again chaps. Any thoughts on how I get the final clutch assembly free? Have removed the use one time only nut and metal washer. 

I recently had to  use a 3 legged puller, through the big holes, to pull the clutch back plate off.

Paul.

It's probably the O-ring holding the clutch basket on.

Pick that out and then the basket should slide right off.

Thanks. Will look for the o ring over the weekend as I didn't take one off... failing that I think there is a puller laying about. 

You can probably see the oil spewing out of the main seal. Any recommendations for cleaning products for the bell housing and also for removing dried on dirt from the clutch housing? Will break cleaner do?  Really surprised at the build up considering the only way in is through the small gap on the clutch arm.

I took off the O ring, picked it after taking off the nut as Duck says, the clutch came straight off then. O ring was bad too but had a new one bought.

I have a few as in I think about 4k miles on the new one now and all is ok.

MMWW wrote:Will break cleaner do? 

Brake cleaner's fine for the oil. You might need to use something else like Muc-Off to loosen the baked-on stuff.

MMWW wrote: Really surprised at the build up considering the only way in is through the small gap on the clutch arm.

There's also the weep hole at the bottom front of the transmission for dirt/dust to get inside the bellhousing.

When I have things apart, I usually use engine cleaner/degreaser and lots of water to clean all of the road grime off of the bottom and back of the transmission. Just be careful not to get water in the transmission via the breather cap on the top.

I did a full fluid change after all was done. I was due an oil/filter change anyway and left it all until it was all back together.

Had to do the clean up to sort the gear position indicator switch, it gets rather messed up with road dirt.

I coated the non mating surface of the switch with Plasti Dip, minimal application around the mounting bolts. And heavy silicone grease on the mating surface. It hasn't missed a beat in 18 years.
Regards Martin.

If it's never been replaced before then the gear position switch is 30 year old plastic in a place that gets exposed to a lot of abuse.  In tearing down old Ks over the years I've had quite a few of them literally crumble to pieces when I removed them.

For ones that are still in one piece I treat the plastic with a product called 303 Aeropsace Protectant which is supposedly one of the better products around for keeping plastic alive.

I still have my original 25 year old one that I cleaned up and coated in Plasti Dip as a back up. You could not pick a worse position to mount a switch. I had cause to check mine about 4 years ago and the Plasti Dip was still fine.
Regards Martin.

I have coated a few in Sikaflex and never had any more problems.

Quick update...

I managed to pick off the clutch o ring which took ages then the final clutch plate just pulled off. I removed the old rear seal using a screwdriver with a hooked edge, leveraging it all around. The new seal is fitted and the leak has stopped!

Now I was looking at cleaning the sprag clutch and the diagram posted earlier of the 17 bolts is helpful with this however so far I've been doing this work working forwards from the rear of the bike. It looks like I will need to jack up the engine with a lump of wood and remove two(?) frame mounted bolts and then the alternator and starter completely from their position. This would then give me access to the bolts on the top of the housing. 

Would the bell housing then have enough room to slide off, or do I need to remove anything else? 


Cheers

Sounds about right. I can't remember if you need to drain the oil first but it wouldn't hurt.

The bolts holding the alternator on will have corroded threads so make sure that you use a good Allen wrench on them and that it is fully seated in the bolt heads so that you don't strip them. Use some anti-seize when putting them back on.

You don't need to drain the oil but you will need to support the bottom of the engine as the rear engine mount is at the top of the bell housing, you may find that oil leaks past the main seal as the engine sags in the frame, I normally jack the engine slightly to reduce the stress on the front mounts and level the engine to prevent the leak.

A note on the 17 torx bolts, they are shallow, I had one strip and had to drill it's head off so take care. I replaced mine with a standard hex allen head.