Question for those of you with factory shop manual

[Justin B.]

I finally got motivated enough to start tearing down the Junkyard '82 LS in an attempt to diagnose it's "mosquito killing" problem.  I was expecting to find stuck or broken oil rings but after pulling down the left hand side the bore is nice and shiny with no felt blemishes, after cleaning the piston looks as close to new as you can find in a used engine, and rings are free and in one piece.  I pulled the compression ring (I love my "vintage" Sealed Power ring expander pliers) and popped it into the bore and measured a .022 end-gap.  This seemed a bit wide to me and the "Somewhat Good Book" (aka Haynes) indicated the range should be .0118" - .0197".  The gap would be within range for a /7 but the r65 is not specified so the values I quoted are from the "All other models" line.

I guess it's time to save up for a set of rings as I feel it would be kinda sacrilegious to put the good set of early sleeved jugs and slugs in - gotta talk myself into believing it's worth putting another $80 (£14.00/set at Moto-Bins) into.    I find it rather odd it was smoking as much as it was, though, for only being a couple thou' out...  Guess I should pull the oil ring and see what it's gap is before I make any further rash statements...  

I measured the end gap on the oil ring (one-piece style) and came up with .0245" which according to Haynes is almost .010 over max so maybe that is the cause for the smoking.  Funny that cold you could rag the crap out of it and not a puff but after warming up for a couple of minutes would smoke profusely when revving and sit there "puffing" at idle.  I guess that makes sense as I would guess the aluminum cylinder expands a larger percentage than the steel ring...

So, if somebody has the factory book I would appreciate it if they could please verify these end-gaps for me.

[Semper Gumby]

Of course the factory manual list everything metric and uses different names for things so I will print all and hope you can figure it out.  

From page 12/18 BMW R65 - R100RT Repair manual....

Top Ring           Height 1.75 -.010 +.022   Vertical Clearance .30 to .50  Flank Clearance .060 to .092
Oil Ring             Height 2.00 -.010 +.022   Vertical Clearance .30 to .45  Flank Clearance .040 to .072
Oil Control Ring  Height 4.0  -.010 +.022   Vertical Clearance .25 to .40  Flank Clearance .030 to .062

Remember these are in Millimeters.  Top ring is number 1 Oil ring is number 2 and oil control ring is number 3.

Clear as mud right?

Hope this helps.

TTFN,

[Ed Miller]

The rings come as a kit and are labeled; I was impressed.  For a hundred bucks or so I should have been.  You probably already know this, but the oil control rings get sharp with use.  I was removing my old ones, no big deal, when I noticed blood all over my piston.  Hmm, that's weird.  I didn't know pistons had blood in them, nor did I remember hurting it.  Oh yeah, it was mine.  I couldn't even feel it cutting my finger.

[Justin B.]

Yeah, all of these are sharp but I have a set of ring pliers so really don't hardly need to touch 'em.  I ordered rings from Moto-Bins, after exchange rate it worked out to about $20/piston.  The exchange rate is heading back to our favor...