Different jugs left to right?

[VaSteve]

I took the cylinders off the engine and in doing so I noted that one had the rubber gaskets on the top head studs and the other did not.  The cylinders had different part numbers so perhaps one of these was replaced.   Which one?  

The right has p/n 82ZNW1 "A..."  this one had the rubber gaskets
The left was  p/n 82ZNW2 "C" the one did not.

Which one is the one that's supposed to go with the bike?   What's the other from?


The left side has most carbon built up on the piston crown and was the one leaking more from the pushrod.   Doubt that makes any difference...

[montmil]

Steve, this is one of the best BMW parts fiche available. Check it out. It seems as if a PO may have swapped out a different jug due to... ?

http://www.ascycles.com/Illustrated_catalog/R65(78-85)/catalog_frameset.html

Monte

[VaSteve]

I use that all the time.  I didn't see any numbers like that on the fiche.  I'll have to look again.

[Bob_Roller]

The numbers you posted are most likely numbers used by the manufacturer of the cylinders, not a BMW part number .

[Rob Valdez 79 R65]

I've never heard of a airhead engine that didn't need the two small o-rings on the two top cylinder studs.  

Did you not have oil leakage where there were none?

Was a base gasket used?  (You don't need one unless you are trying to modify something, like compression ratio).

These are all words of a non-professional mechanic.  Take care!

[VaSteve]

the clymer said it could be either way (with or without).  I didn't expect it on the same bike.  The side without had the leaks but they were at the bottom. Of course.

[Rob Valdez 79 R65]

From what I see on RealOEM fiche, the small o-rings were introduced in production month 7/1976 with the /7 series.

If you don't have them, I would put them in.
Make sure there is a space for them (not sure if it is on the block or the cylinder, and after reassembly, but BEFORE putting the valve covers on, remove the spark plugs, stick them in the caps, laying on the cylinders (grounded), and turn the engine over with the starter motor until you see oil coming out of the rocker towers.  This last part is a given after doing any major or unusual work on the engine!


These are the only pictures I have from when I had the heads refurbished on the 1980 engine I had in my bike at the time.  It looks like most of the recess is in the cylinder.  Can't really tell about the case.
But you can!

[Lucky_Lou]

My 79 has the "O" rings on both sides perhaps someone missed them on a previous strip down.
Lou

[VaSteve]

OK, I fail at this.  When I took off the second one, the rings stuck to the cylinder and I was in a lot of pain* anyhow so I never looked closer.  I went out to shoot a photo for you all and upon closer inspection, the rings went with the cylinder on that side.  In this photo you can see how flush they were (far right)   Crisis averted.  


* I got the piston pin out halfway (off the rod) and managed to slam my finger (and break the skin on the piston skirt) pressing the rest of it out on the workbench.    Now it's all bruised and cut up.

[Rob Valdez 79 R65]

Wow - sorry for your pain.

Why did you take the pistons off the connecting rods?

[Justin B.]

Why did you take the pistons off the connecting rods?

Some prefer to do it this way feeling it's easier to leave the pistons in the bore then fiddle around with the rings when reinstalling the jug.

The numbers referenced are likely casting numbers where the A and C are bore sizes...  I think the jugs were sorted by size (A, B, C) and I think were supposed to be installed as pairs of the same size.  Possibly your engine's had a jug replaced?

[Rob Valdez 79 R65]

Some prefer to do it this way feeling it's easier to leave the pistons in the bore then fiddle around with the rings when reinstalling the jug.

But he pulled them out, anyway!

[VaSteve]

Wow - sorry for your pain.

Why did you take the pistons off the connecting rods?

They looked so sad flopping around without the cylinders.   It's going to be apart for a while and I will put it back into the frame disassembled.  I figured it would be one less thing to worry about.

Some prefer to do it this way feeling it's easier to leave the pistons in the bore then fiddle around with the rings when reinstalling the jug.

Didn't think of it this way, but I guess I could reassemble P&C on the workbench and slip onto the case.  Would that work?  I don't have a ring compressor (yet).  I didn't expect the rings to be as loose as they are.  

[Rob Valdez 79 R65]

I've never needed a ring compressor to put the pistons back into the cylinder.  I just do one ring at a time.

http://w6rec.com/duane/bmw/piston/ringtool.htm

[VaSteve]

ha!  This is great.  The book showed a tool.  Thanks!
The only time I took apart a car engine it didn't go back together.