Forum bmwbike.com

I saw a thread on the past 90 days
ones regarding the original oil control rings not working. I have R69 5 ring pistons fitted in my R69S.I just had the cylinders re-sleeved, fitted new rings(including a chrome top compression ring, and a 2nd stepped ring) but 700 miles of running have not improved the oil consumption of 100 miles/pint. Has anyone any ideas why this is happening? In old days these BMW's did huge mileages on the original oil rings, so why the non-working now? If I fit a replacement of the multi-segment "new" type rings will this cure the problem?
Any suggestion gratefully received.

I am not sure what you mean by 5-ring pistons. The pistons have 3 grooves. The bottom groove is for the oil ring, and this ring can have either 1 or 3 peices.
My Huggett pistons came with 1-peice oil rings that did not break in - they burned a huge amount of oil, and made it impossible to start the bike. I installed new ring sets wit the "new style" 3-peice oil rings, and they broke in immediately. It sounds like you should do this, too.
I think it is very difficult to break in the 1-piece oil rings in a boxer motor because lubricating oils are so good that not enough heat and wear is generated.

Allan,
Thanks for your reply re above subject. Point taken about lack of bedding in. in a boxer motor. When I said 5 ring I mean the piston has 3 compression rings, and 2 oil control rings, including one below the gudgeon pin. The reputation was that these old pistons ran extra quietly as the bottom oil ring made the piston sit more squarely in the bore. If I fit the all bells and whistles new rings, how difficult are they to fit?(assuming one is fitting a barrel onto a piston in a motor installed in the bike, meaning a sideways grip of the barrel while persuading the rings to slide in)

Jon,

If you have the propper ring compressor (strap type) it's as easy as 123 even without a helper. If you are trying to fit by hand, I wouldn't even try....especially that 3 piece oil ring. Make sure you get the proper instructions for assembling the latter as manufacturers differ even though the pieces look the same. I am referring mostly about the orientations of the gaps in the 3 piece ring.
I purchased mine from Mark but have yet to kick the engine over...perhaps on the weekend if all works out well. I have an R69S (1967) with 1st oversize. Also, what is important is to space the gaps evenly and don't mind where the oil ring gaps end up with respect to the base of the bottom of the cylinders as all the rings rotate in time. The probability of all the gaps lining up at one point during the life of your engine is slim but it does happen...this is when owners start noticing higher oil consumption and blow back (dirty oil) through no fault of their own......nothing is perfect even on a Bee-M.

Pierre

You may have unusual pistons - I only remember 3 grooves and it sounds like your pistons have 5 grooves. You might have trouble finding ring sets for such pistons.

I watched as someone else installed my new style replacement rings ( having the 3-piece oil rings) with the motor in the bike. He used a strap compressor, and it only took a moment. But he had done it many times.