787 rebuild - ring end gap out of spec?

[poissonn]

Hi, I'm currently rebuilding the 787 in my '97 SPX.

My local machine shop bored & honed the cylinders 0.5mm over using WSM pistons. The wall clearance is roughly 0.0047"-0.005", which right around what WSM calls for on their spec sheet (0.0045-0.005).

However, the ring end gap on each cylinder, with all 4 rings is 0.020"-0.022", which is a bit more than their spec sheet (0.010"-0.018"). Should I run these rings anyway? Any concerns on power/compression?

Since both sets of rings have the same gap, I'm thinking even if I try new sets, they'll all end up with roughly the same end gap.

 

[etemplet]

Install the rings and don't worry about it at all. Everyone I get is like this. Compression will be great !! Good idea to check though. I rarely see less than .018" gap on the rings. Perhaps they are allowing for the ring to expand... either way... you're good. Ride it like you stole it... after proper break-in of course. LOL Good Luck.

 

[Ckrawiec]

Hi, I'm currently rebuilding the 787 in my '97 SPX.

My local machine shop bored & honed the cylinders 0.5mm over using WSM pistons. The wall clearance is roughly 0.0047"-0.005", which right around what WSM calls for on their spec sheet (0.0045-0.005).

However, the ring end gap on each cylinder, with all 4 rings is 0.020"-0.022", which is a bit more than their spec sheet (0.010"-0.018"). Should I run these rings anyway? Any concerns on power/compression?

Since both sets of rings have the same gap, I'm thinking even if I try new sets, they'll all end up with roughly the same end gap.

Just an FYI: Not for nothing but according to the 97 Service manual...the '97 SPX is spec'ed for a 1st overbore to 82.25MM. There is NO spec for a second over bore....therefore, your 1st overbore is already beyond the Seadoo spec.

The ring end gap spec is 0.25 to 0.40 mm.

 

[poissonn]

Install the rings and don't worry about it at all. Everyone I get is like this. Compression will be great !! Good idea to check though. I rarely see less than .018" gap on the rings. Perhaps they are allowing for the ring to expand... either way... you're good. Ride it like you stole it... after proper break-in of course. LOL Good Luck.

Thanks, this is good to know! That's the information I was having a hard time finding on the forums

 

[etemplet]

I never to the seadoo spec overbore. I always go to .5mm. Leaves more meat to clean up the bore. Touchdowns everyone !!