Oil leak between cylinder and head

[fig]

I have a '73 R75/5. Both cylinders are leaking oil where the heads and cylinders meet, looks like from the bottom stud (the one embedded in the cylinders). What can I do to stop the oil leak and is indicative of any particular problem, like studs pulling from the cylinder or case. Thanks.

DF

[Airbear]

Hi Fig. It would be useful to know how many miles the bike has done, and if any head work has been done previously.

My head to barrel joints were slowly oozing oil for the last 3 years or so, recently fixed. Not really a problem if that is all that is wrong. The fix is to replace the head gaskets. In the process you get to check for things like pulled studs, valve recession and so on. My suggestion is to check the torque on the head nuts before undoing them. You will need to use a known-good torque wrench and know the prescribed setting for your model. Carefully tighten to that torque, maybe going an extra foot-pound or two more if necessary. If there is a pulled stud it should be immediately apparent.

If all is well, remove the rocker gear (take photos and label carefully, noting orientation of all parts - you really want to put everything back where it was). Fit new head gaskets and torque it back up (there is a sequence for this), fit rocker gear, adjust valve clearances and you are good to go. The Clymer manual has good instructions and pictures. While you are in there, you might feel adventurous and want to go deeper, checking pistons, rings, bores, etc etc. Be warned that the deeper you go the more expensive the job is likely to become.

The above assumes you have access to tools and are at least somewhat experienced with their use. The job is not all that difficult and you will gain a comforting intimacy with your bike. Good luck, and if you need more info, just shout.

Also, it's good to do some on-line research - google '/5 head gasket' or some such.

Edited to add: If you decide to just remove the heads, apparently it is possible to tie the cylinders to the engine with rope, wire or whatever to avoid breaking the engine to cylinder base seal.

[Kurt in S.A.]

Don't the /5 have o-rings to seal the exposed tubes? See Anton's discussion here:

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

Kurt in S.A.

[fig]

The Bike has done 66,000 miles. I've owned it 7 years and have only put about 4000 miles on it, the previous owner had the heads redone at Bob's sometime before selling it. I think I'll clean it up really well and re-torque the heads to start with and see if it continues to leak. If it continues to leak I'll pull off the heads and replace the gaskets. I was thinking the studs maybe pulling because the last time I adjusted the valves the intakes had tightened a bit, maybe a thou or so. What does a recessed valve look like, how does one check for that?

Thanks

[lrz]

Odd for the intakes to tighten or recess, generally that is on the exhaust side. If your heads were reworked at Bob's, probably by Bud Provin, and especially with 66,000 total miles I doubt that is the issue.

OTOH, after re-installing heads and gasket it is at some point necessary to re-torque. Obviously, you cannot properly set valve lash until afterward.

The 6:00 and 12:00 studs do not go through to the case.

[Airbear]

I was thinking the studs maybe pulling because the last time I adjusted the valves the intakes had tightened a bit, maybe a thou or so. What does a recessed valve look like, how does one check for that?

Fig, stud pulling would open the valve clearance. Recessed valves are indicated by tightening clearances over a period of time. One thou could be user error, but worth taking into account when you next check them. The valve seat is what gets pounded, and the valve head 'recesses' into the seat. I don't think you have a problem, and re-torquing the heads may even fix the leak. Good luck.

[fig]

Thanks for the responses everyone! I'll try the re-torquing first and see what happens.

DF

[Jean]

Heads should have been retorqued after about 500 miles!!
Also, check torque BEFORE doing the valves...each time.

[fig]

Whats the consensus on re-torquing, backing off till loose and torquing in stages until proper torque is reached or checking if they're at the proper torque setting from where they are now?

[Major Softie]

Whats the consensus on re-torquing, backing off till loose and torquing in stages until proper torque is reached or checking if they're at the proper torque setting from where they are now?

It is not possible to "check if they're at the proper torque setting now" (slight paraphrase there). If they have been tightened to the correct torque, it would now take a significantly higher torque to break them loose. So, the only way to "check" the torque on any bolt is to back them off and re-tighten. IOW's, you can't/don't really "check" them, you just re-torque them. The only thing "checking them" can catch is if some have become WAY too loose.

Now, the proper technique for that actual process is where we might be able to get an argument started.

You can find Snowbum's recommendation here: http://bmwmotorcycletech.info/setvalves.htm