Forum bmwbike.com

Does anyone know for sure if the oil ring gap orientation on a horizontally opposed twin is important? ie. Should the gap be placed at top bottom or side or does it really matter as long as all the ring gaps are spaced equally along the piston circumference.

Hi Pierre,

Here is something which I have uplifted from another site.

''Fitting New Piston Rings. On all boxer engines, never fit an oil control ring gap facing down, as when the engine is stopped after a run, oil can collect in the bores and seep through the end gap. Also remember to separate the three gaps to 120'. ''

This makes sense but don't ask if they move around afterwards!

Regards

Frank

Thanks Frank,

After an exhaustive 3 week search, the consensus is that the orientation of the oil ring gap with respect to the cylinder is unimportant as the rings turn, especially during break-in. Average spin is 5 RPM. As for the two rail pieces, their gaps should be 180 deg apart (the ones I have anyway). A different manufacturer (Total Seal) recommends putting the gaps 1 in. apart on each side of the wrist pin. From what I learned during this exercise is that if it is logic it is ok. (sometimes better than what the manufacturer recommends although I would follow the recommendations if indeed the piston and rings came with a set of installation instructions which in my case were nil!