Vintage BMW Motorcycle Owners

I have a '74. A Lot (20+) years back my mechanic pulled & reput the heads, can't remember why. Shortly thereafter, both right side rockers were so tight as to cause mis/back firing. Mech reset them, but problem returned within 10 miles. Reset again, returned again except this time it broke both of them right at the adjusting bolt. Mech and me both clueless as to cause, so the bike sat.

I'm finally able to pursue this, having done a Lot of bike work in the meantime. The mechanic passed away a few years ago. I was thinking I "tuliped" the valves, me being just stupid enough back then to not recognize the problem and that a '74 needs lead additive for unleaded gas. I bought a set of '75 heads to swap and relegated myself for lead additive from now on.

The issue: I pull the heads and compare both sides with the bought set, I Can't See Any difference. The valve disc and keepers are visually at the Same distance on all 4 heads and the valve shapes & concaves are the Same too. But when I pulled the right head, it was so "bound" on the low side, I had to slowly pry it off. The stud in the low side middle had gasket sealer all over it, And No thick washer ! The left side had both washers, but right only had upper.

Question, could the missing washer cause the problem? If so, how? If not, what should I be chasing?
Thanks in advance... Kevin / SW Mich

Welcome! I'm not sure I can follow the issue with being "bound", etc. But I don't think your valves tuliped. For the pre 1981 models, the issue was that the valve seat receded or wore away, thus closing up the clearances. For the '81-84 bikes, the seats were changed but to stainless steel which didn't conduct heat. That heat stayed in the valve faces which actually did deform or tulip.

But let me ask so that we can all go from there. Were the valve clearances set with the right side cylinder at top dead center on the compression stroke? It's a little different, but there are numerous situations were the mechanic rotates the engine so that the left cylinder shows the TDC mark in the window...and maybe gets lucky that it is on the compression stroke. Then, without rotating the engine 360 degrees, they go to the right side and set the valve clearances. In truth what this results in the left side with proper clearances and the right side with huge clearances. It's possible I suppose, if one can get past the loud clatter on the right side, the extra pounding could break off a rocker arm.

Beyond that, I suggest reading this website on rockers and heads over the years. See if there's something here that might help point to an issue:

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

The '76-on rockers are different than the '74/75. If you bought some '75s to replace your originals, they would essentially be the same.

Thanks for the clarification, seats vs tulip. Indeed the clearances tightened dramatically and in a short time. What I don't get is, wouldn't the valve stick significantly further into the cap area, I mean noticeably? Or are the distances too small enough to see.

I'm still caught up on the one washer on bad side and both washers on good side. The "bound" was all the gasket goo around the lower middle stud. I suspect the missing washer allowed the leak and the "mech" packed it with goo instead of fixing it right.

Thanks for the link too. I've got some checking to do, looks like all 4 shafts were upside down. Maybe just reassembling what I have Correctly will "fix" the problem.

Way to many problems. Now that you have 2 used heads before use put them on. I would take the valves out and have them checked and the valve seats. You want to make sure the valve steams are straight also. Replace the valve guide seals, make sure the heads are flat, the exhaust port threads are good, have all 4 washers/ head gaskets handy. Pull all 4 push rods out, make sure they arent bent and the right length. i wouldnt take the sellers word that they are OK. Most of this stuff you can do yourself. Get the book out to make your adjustments. If you dont have one....why not? A good mechanic always has a good book handy....or more. I have just over 100 books for every car or bike I ever had. And never sell them. Hey I never know if I might get that same vehicle again.

twocams

Hi, 3 years later, problem found !!
Idiot mech put 3 of the right side head nuts on BACKWARDS !
The locking side of the nut is ~.060-.070" high and of a much smaller diameter.
Running the engine progressively "mushroomed" that smaller diameter, so the valves opened up.
Resetting just allowed it to happen again until the rockers broke.
I only found this recently when refitting rebuilt heads and finding 3 nuts that a socket won't fit over the "flange".
The "AH HA" moment was a flashbulb.
I post this just in case somebody else runs into this issue.

Glad you persisted and found the problem! Guess I'm not quite familiar enough with the nut issue and that it has a proper side for installation.

Can't 'mem proper term, but it's self locking by a smooth smaller diameter that's been compressed to squeeze the threads.

I don't remember any self locking head nuts...but I have a /7. I notice in MaxBMW's website they say the following for the four head nuts:

- 11 12 1 261 775 HEX NUT (to 09/75)
- Fit 1970-1975 models. In many 1974 models, they were not properly hardened.

So maybe you were the unlucky one to have nuts that just mushroomed because they were of poor quality.