Ring End Gap Spec on 717 Engine Piston Ring

[rkunkel39]

I'm rebuilding top-end on 1999 SeaDoo GTS with 717 engine with 0.25 mm oversize pistons. One cylinder was good on compression and the other was bad. The bad cylinder had a broken piston ring. I was checking the piston ring end gap (top ring) on the good piston and it was larger than 0.039-in, the wear tolerance in the manual. Out of curiosity, I measured the ring end gap of the new piston ring and it was larger than 0.039 inches. The manual says the new ring end gap should be 0.016 to 0.022 in. Is this something I should worry about? Did I get the right piston rings? I bought a new WSM piston with rings because the old piston had a gash underneath the piston groove.

As a side story,the bottom ring on the good piston was stuck. I tried to get it out to measure the ring end gap but broke it. Had to pull the piston and it is now soaking in mineral spirits. I'm going to end up buying new rings for that one anyway. I'm not sure how that cylinder had good compression. I guess the top ring was doing a good enough job.

 

[Dr Honda]

Are you using WSM rings in the OEM piston?? If you are... take them out. Not everyone designs the rings the same. Also... if you are using and aftermarket piston/ring combo... you need to use their clearance specs, since they may use different materials that the OEM parts.


Finally... if you are going to use OEM parts... and you have a 0.039 gap, and it's out of spec... then yes... you need to get different rings. A large gap will allow too much blow-by past, and can cause issues. Also... your power will be lower than it should. Good rings can make a huge difference in power.