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Piston rings

Piston rings


Matching piston rings to a new or rebored cylinder


1. Push the pistons rings down into the cylinder one by one, using a piston to position them correctly.

2. Measure the ring gap with a feeler gauge as shown. If necessary, widen the gap by means of a special file. Refer to the "Technical data" section for correct gap sizes.


Matching piston rings to a worn cylinder

Piston rings for a worn cylinder should be matched in the same way as for a new or rebored cylinder, but they must be tried at the lower limit of piston travel (BDC) as the bore is narrowest at this point.

Fitting piston rings on pistons


Use a piston ring clamp to fit the rings as shown. The lower compression ring must be fitted with the side marked "TOP" uppermost. Check the fit of the piston rings in their grooves by rolling them round the grooves. Also measure the clearance at several points.

Oil the piston and rings before assembly. Turn the compression rings so that their gaps are roughly 120° to each other and position each of them above one of the gudgeon pin holes. Also make sure that the gaps in the top and bottom rings of the three-part scraper ring are staggered round the piston and not in line with each other.