Hi all. Did an engine swap on my k100 ('84). Put in a similar age engine which seemed ok. Put in new 'monkey nuts', new cam chain.  After starting up, there is an ocassional loud clang from the alternator side of the engine. It sounds like something is hitting the engine case. Any thoughts? Also, the throttle bodies are now slow to return after opening the throttle and the cam chain sounds quite rattly. Many thanks, Dave.

Very easy to remove the right hand engine cover to get a look at timing chain.

Happy the alternator monkey nuts are ok?

Yup - sounds like you managed to get the alternator mounted 30 degrees out i.e. the drive flanges did not go down the middle of the monkey nuts. There's a cast mark on the flange cup to help you line up with the centre of the monkey nuts - it can be a real bugger to push the drive flanges into new nuts, so I usually smear the nuts with silicon grease.

cam chain rattling sounds like the teeth on the chain tensioner  mechanism have become rounded (deep inside the tensioner )  letting the tensioner backlash down to minimal tension of the bow spring runner across the length of the cam chain guide  which seems quite common on older engines

don't know the solution other than changing the tensioner  but willing to experiment , have an issue in re case hardening after modification though  no heat tools suitable  here in my awning workshop ...giggles '


good luck with the solves

Thanks chaps for the input. Dai, I did think that maybe I hadn't done something right with the alt'. I'm about to go into the garage and check it out. Thanks once again, Dave.

I bought a timing chain kit for the K100RT but I also got the tensioner with it. I thought it was advised to change it with the chain on older Ks. Mine has 89,000 miles.

Hi Olaf, I didn't get the tensioner, probably should have. Dai, I checked the alternator nuts, all was fine, but it's still making a lot of noise. When I swapped the motor over, I also put in a new alt bearing. When I first put the motor back in the frame, then put the alternator in, it wouldn't go all the way onto the drive dog. Closer inspection showed that the bolt i used to hold the drive dog on was too big and was stopping the alternator from sliding home fully. I took it out and replaced it with a correct size bolt from a spare engine. Could something have gone amiss on the inside of the bell-housing when I did this? Cheers again, Dave.

Only if you pulled the alternator up hard with the wrong bolt in. If you realised there was something up before you got to that stage then you might be okay. Best thing to do is... pull the alternator and have a look inside with a torch.

Thanks for the reply Dai. When you say pull the alt and look with a torch, do you mean pull off the drive dog and peer into the bell housing through the hole? I'm a trifle reluctant to take the motor out again, pull the clutch and bell housing, although if that's the only option...
Thanks again, Dave.

Having checked this:

http://www.realoem.com/bmw/enUS/showparts?id=0511-USA-04-1984-K589-BMW-K_100_83_0501,0511_&diagId=11_4686

- I'm beginning to agree more with the others that if you didn't pull the alternator up hard with the wrong bolt, then the cam chain may be the problem. If the metallic slap occurs on a sudden throttle-off it's a good pointer that the cam chain is the problem. As Charlie says, pulling the righthand crankcase off to get access to the bottom drive gear of the chain is an easy job...

http://www.realoem.com/bmw/enUS/showparts?id=0511-USA-04-1984-K589-BMW-K_100_83_0501,0511_&diagId=11_1774

(item 7) but if it's never been off before I'd be inclined to get new sealing rubbers and a gasket. The only time I didn't do that LFB pissed all over the floor on startup. If the chain lifts free of the gear then most likely it's fooked, but I'd rather someone who has had that problem chimes in here and specifies just what is acceptable.

Thanks Dai once again, cheers, Dave.

You can fire up the engine with the alternator off.......try that and see what you get.

Dai wrote:Yup - sounds like you managed to get the alternator mounted 30 degrees out i.e. the drive flanges did not go down the middle of the monkey nuts. There's a cast mark on the flange cup to help you line up with the centre of the monkey nuts - it can be a real bugger to push the drive flanges into new nuts, so I usually smear the nuts with silicon grease.

I'll second that Dai but even with grease the rubber dampers still try to close together when you (try to) push the alternator into position.

Thanks Olaf and Mike, I'll give that a try also. Cheers, Dave.

Motorbike Mike wrote:

I'll second that Dai but even with grease the rubber dampers still try to close together when you (try to) push the alternator into position.

I don't even bother to try to push them in after fighting new nuts twice (different bikes). On the third one I made sure everything was lined up, put in a couple of bolts that were way too long (top and right) and drew the alternator in that way. Keeping downward hand pressure on the alternator substituted for the 'missing' third bolt because I was too lazy to fiddle one in. You know when the alternator is in because the bolts suddenly start winding in really easily; at that point a good shove will seat it and you can put the correct length bolts in. It takes less time to do than it does to describe.

Dai wrote:

Motorbike Mike wrote:

I'll second that Dai but even with grease the rubber dampers still try to close together when you (try to) push the alternator into position.

I don't even bother to try to push them in after fighting new nuts twice (different bikes). On the third one I made sure everything was lined up, put in a couple of bolts that were way too long (top and right) and drew the alternator in that way. Keeping downward hand pressure on the alternator substituted for the 'missing' third bolt because I was too lazy to fiddle one in. You know when the alternator is in because the bolts suddenly start winding in really easily; at that point a good shove will seat it and you can put the correct length bolts in. It takes less time to do than it does to describe.

I'll try that if there is a next time.
I must admit that I didn't think of using the bolts to help the alternator back in.
I'm a gentle man with loving hands you see.