R90/6 Rocker Arm

[achart17]

Hey guys,
Brand new to the group. Im restoring a 1976 R90/6 and noticed my rocker arms are shimmed with one shim between the rocker arm and arm support. When I look up the parts on MAXBMW.com they claim a shim is not supposed to be used with my arms. This is weird to me because each arm is shimmed on the motor. If they are required i need to purchase two. Anyone have any experience here?

 

[20774]

Welcome to the forum! Nice bike the '76 R90/6!

Any info from the previous owner? But as you're finding out, that's not standard. Anton has a good description of rocker arms by period:

http://largiader.com/tech/rockers/

Probably what was going on is that the PO was hearing a bit more noise coming from the valves. What's typically done for that is to squeeze the two blocks together when tightening the head bolts. Duane Ausherman has a procedure for setting valve clearances on this page:

https://w6rec.com/bmw-motorcycle-valve-adjustment-procedure/

In step 11, he shows a pair of channel locks used to keep the blocks together. I find that a bit extreme. When I do it, I just use my fingers to hold the blocks tight and then run the torque up a bit, enough to hold the blocks. Torquing is in stages...maybe 15 ft-lbs, 20 ft-lbs, finally 25 ft-lbs. All the bolts in the head should be done in a criss-cross pattern.

Another site for information...get to know it's there by Snowbum:

https://bmwmotorcycletech.info/technical-articles-list.htm

Here's his article on setting the valves...he also mentions channel locks:

https://bmwmotorcycletech.info/setvalves.htm

When done, you don't want a lot of movement in the rocker arms as you try and move them up and down. You should see some oil film changes as you move up and down.

 

[PGlaves]

Somebody went the extra mile to get the rocker arm free play where they wanted it. Sometimes this isn't necessary. Sometimes it is. Usually it is ignored and a little extra clackity clack happens. If when the head studs are properly torqued the end play is within specifications and there is no binding of the rocker arms you are fine.

 

[RPGR90s]

rocker arm endplay

Hey guys,
Brand new to the group. Im restoring a 1976 R90/6 and noticed my rocker arms are shimmed with one shim between the rocker arm and arm support. When I look up the parts on MAXBMW.com they claim a shim is not supposed to be used with my arms. This is weird to me because each arm is shimmed on the motor. If they are required i need to purchase two. Anyone have any experience here?


View attachment 78032

View attachment 78033

Try and shoot for about .004" or less freeplay in the up/down movement of the rockers and you'll have minimal clacking.

 

[lkchris]

For the very last Airheads, say 1985 on, BMW went to extra effort to make these engines quieter, and this included rubber pucks between the cylinder head fins and new, shorter rocker arms with shims, which iirc were nonmetallic, i.e. nylon or some other synthetic.

 

[achart17]

Really appreciate the quick replies! I'll see if I can get them within spec without the shims.