Top end rebuilt? Is it time?

[rkkoeb]

I have a 1997 Seadoo GTS and did a compression test. Both cylinders are showing 120. When is it recommended to do a rebuild? Jet ski runs great but with the end of the season coming soon I was thinking if I need to rebuild the motor it would be a good time to do it.

Thanks

 

[XP 787]

I would do another test with a different gauge just to be sure before you start doing a top end.

 

[MacAddict]

Make sure you do it with a good gauge, SnapOn, MacTools, etc..... spark leads grounded and throttle wide open with GOOD battery

 

[rkkoeb]

I used my buddies snap on gauge when I did the test and yes throttle wide open and spark leads grounded. Do you feel that 120 is low? If so what brand top end kit does everyone recommend using?

 

[MacAddict]

I believe stock it should be banging 145psi+.... so yeah she's pretty worn out @ 120psi.

Hands down I would recommend www (dot) fullboreonline (dot) com. Dan absolutely knows his stuff and his top end kits are solid as hell. Have done 4 different engines and top ends with him, and his work is solid.... plus great tech advice... and make sure you do the rave valve trim to account for new bore clearance

 

[rkkoeb]

What are the "Rave Valve Trim" Do I have them on a 717?

 

[MacAddict]

Sorry sorry... saw that other guys handle and thought this was 787... if it's a 717 there's no rave valves...

 

[1969iggy]

Why throttle wide open when you do the test? I've done them without touching the trottle... when the PSI is 25 and 125... it does't really matter how accurate it is i guess.. but i have one with 130/130 and i'm in the same boat.... (or in the same seadoo...)

 

[dean.mohr]

What are the "Rave Valve Trim" Do I have them on a 717?

When you rebuild a top end, if you go with a slightly larger bore, the RAVE valves (variable exhaust valves) will stick too far into the cylinder and the pistons will hit them. So you have to physically trim back the RAVE valves to ensure they don't hit the pistons.

However, with a 717, you don't have RAVE valves anyway, so not a big deal.

 

[dean.mohr]

Why throttle wide open when you do the test? I've done them without touching the trottle... when the PSI is 25 and 125... it does't really matter how accurate it is i guess.. but i have one with 130/130 and i'm in the same boat.... (or in the same seadoo...)

You should always have the throttle fully open so that you get a full charge of air when doing a compression check. If you don't, you could read slightly lower compression than you have only because there is slightly less air in the cylinder.

 

[rkkoeb]

Can you rebuild the top end of the motor leaving it in the jet ski?

 

[MacAddict]

On that motor? Absolutely.... the 951 motors are tricky to do in the ski, but entirely possible with rubber band trick. On yours, just be sure to align the jugs properly but putting the exhaust manifold on fairly snug (not all the way tight) after dropping the cylinders on top of the cases. Don't tighten the bolts into the cases to secure the jugs until the exhaust manifold has been snugged up and everything aligned. I recommend using some loctite 518 anaerobic to seal things up as well. Not loctite red permanent. .. use 518.

 

[rkkoeb]

Going to put the carb back on this week and see how it runs. If it runs good I will most likely hold off until next spring to rebuild the motor. With that said what is the recommended number of turns out for both the high and low screw for the carb?