Boxerworks.com

Hi i am new here and new to airheads (beside growing up with them). A couple of months a go I finally bought my first Bmw boxer and I am glad I found a '76 R100RS (imported from Switzerland 15-20 years ago I think) and it is nothing like the Japanese bikes I own and love. It has been stored away for 15 years so it needed som work. I got it running, it took some work but one of the things I can not get sorted is a rattle at 3000rpm under load. Nothing at idle and nothing beyond 3400rpm. I feel it runs strong. It comes from the left side of the engine, I thought it was the timing chain since it was coming more from the front than middle of the engine.
I met a guy who has the same rattle but only at idle, he says pushrods. When changing head gasket and pushrod tube seals I re installed the pushrods looked fine and so did the lifters. Camshaft looks good. Isn't the pushrods rotating all the time ? They seemed fine and straight.
Can I adjust the tubes ? I will pull the rods to check if they are bent.

Any experience with this is welcome !

If the head gasket is installed wrong, part of the gasket will extend out into the tunnel for the rods. The rods could touch the head gasket...it would leave scuffing marks on the side of the rod.

Do you hear the same sound with the bike on the center stand in the driveway? Might be easier to locate the source of the sound.

Kurt in S.A.

Thank you for your reply Kurt !
The head gasket is installed correctly and I did check it when I had to repair 2 studs in the case when reassembled.
I can only hear the sound when the bike is under load...

It does not sound like pinging to me, it really does sound like metal to metal. I did not put the lower half of the fairing on since it is going of completely soon anyway and it sounds the same. I have been everywhere tightening stuff and I really did think it was the side stand against the muffler but I wrapped it with tape and it made no difference.

Nice having you on board. A couple of things come to mind, when you assembled the rockers did you adjust the end play on the shafts? Have you pulled the mufflers and shook them, could it be a baffle that has come loose?

Nice to be here! I have used this forum and the knowledge a lot the last month!

I did adjust the end play on the rocker arms.
And I have had the exhaust off to put some SS mufflers on, nothing rattling in there.

Maybe I should make a list of the things I have done;

New clutch friction plate and diaphragm.
New crankshaft seal and o ring behind the flywheel.
New head gasket and o rings on the cylinder studs.
New timing chain tension gear.
Changed ALL the seals I could find beside the output shaft on the transmission.
All fluids and filters changed.
Checked for play in connecting rods and they are good.
Checked rings in bores and they read as new.
Do worry about the oil rings since it makes a puff of smoke on startup and acceleration from left muffler.

I had the heads apart and found them to be in very nice condition. The PO have had it converted to use lead free gasoline and they must have changed the guides.

Pinging was my guess, too. 3,000 rpms is a bit low to have it under much load. But an R100 should be able to pull harder than my R65. I think, I've never ridden an R100 very far.