Posted May 28, 200816 yr I have a 81 XS 400 with bad rings. I tore down the top half of the engine to change them, but the size isn't marked anywhere on them. I was wondering if anyone knew what size the standard piston or rings are. I miked the piston and I am getting 68.8 to 69mm is that the standard or is it oversized?
May 28, 200816 yr Moderator I have a 81 XS 400 with bad rings. I tore down the top half of the engine to change them, but the size isn't marked anywhere on them. I was wondering if anyone knew what size the standard piston or rings are. I miked the piston and I am getting 68.8 to 69mm is that the standard or is it oversized? 69mm is quoted as standard, so iwould assume you are on standard. the overbores go up in .25mm increments
May 28, 200816 yr Author 69mm is quoted as standard, so iwould assume you are on standard. the overbores go up in .25mm increments Thanks.
May 28, 200816 yr You should also check to see if the ring grooves on the pistons has opened up allowing too much ring movement.
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