Hi,

My name is JC and I am in Brisbane, Queensland, Australia. I've just acquired two k100's and one sounds like it need a bottom end rebuild.

I'm looking for some guidance on what (at a minimum) I should be looking to replace and what else I should do while I pull the bottom end out.

I am assuming I can pull the bottom end out without removing the motor/gbox assem. from the bike?

Is there an off the shelf bottom end rebuild kit I can buy? Do I need to buy rings if the compression is good (noting that they're £20 a piston). I was just thinking main bearings and big ends?

Thoughts? Any advice? I searched "rebuild" and looked in the how to before posting here.

Regards,

JC

Welcome to the forum firstly.
Ks have a real bad habit of noisy drive shafts when some rivits start coming loose. They hold the gear to the shaft basicly and there are 6 rivets which is 1/2 of what is needed.
Dont be in a big hurry to do a crank and big end rebuild a secondhand engine is far cheaper and they don't give much trouble besides the rivets.
Check to see if the noise goes when it has warmed up and that is the usual sign of the bad rivets although they do get bad enough so they rattle all the time and that is getting to the urgent stage.
I cant recall seeing a brick with a shagged bottom end it is very unusual.
If you remove the crankcase cover on the right side then you can get a sight of the rivets which are on the gear behind the gear which is part of the rear counter ballance. 5th gear and work the rear wheel back and forth will show movement that is not supposed to be there although the rivets will make a racket without being obviously loose.
If you do need a bottom end I have several here that you can have but a second hand complete engine can often be cheaper than a set of bearing shells.

welcome aboard jc ...

good luck with the fixing ...probably output shaft is the issue they do get noisy and sound like something lower down in the engine, especially at idle ....once the revs are up ...no real issue

might be an idea to head over to the "introductions" area and post in there ......that and a few more posts will give you access to the downloads section ...need i say more ?



cheers

Wow thanks for the quick responses.

On start up it sounded like a knock but did not continue while the motor ran. I figured with it having 245,000(!) k's on it, it was probably due for a rebuild. I appreciate your advice and will pull the bottom end cover and check out the rivets. The whole thing needs a going over as you might expect with that many k's.

charlie, I'll move the technical discussion to the technical area. This was in introductions. There was a warning there that said I needed to introduce myself before it would let me post elsewhere. It must be our fearless leader's desire to see us bikers compliant that made me comply.

JC

245000km is not a hell of a lot for a K there are quite a few around with 400000km on them and at least one that I know of has over one million miles on it.
On the portal page there is a link to "So, you've just bought a BMW what now" Have a read, Ted has done a wonderful job of putting together a good intro to Ks for a novice. It's well worth a read.

I wouldn't bother with a rebuild. There's plenty of good used engines floating about that in the end will cost you much less in time, expense and effort.  JM.02

My friend is an ex BMW man. In all his time he has never rebuilt a K engine for maintenance, not even a cylinder head off. The only time he has done it was due to accident damage. The engines are unburstable, three things you may end up doing; the oil/water pump, the cam chain tensioner and the 6/12 rivet shaft job as was pointed out. High miles is not a problem.

Hi JCK100
and welcome aboard.
I'd have a look at the cam chain/tensioner. I have a 91 RT/LT (different numbers) with a seriously noisy rattle
and when I took the valve cover off (L/H side cover) to do the valve clearances, I could see where the cam chain has been rubbing on the valve cover inner (shouldn't be anywhere near there). So I need to get brave and see what's happening with the cam chain.
Good luck with it.

thanks jc ...yep didn't notice the post was in the introductions section ...seemed sensible that it was in tech

all good