update (seadoo not going over 4000rpms)

[irish88]

97 787 so i did a compression test and 50psi in both ,take off the (head) and they both look good after i did the top end rebuild the boat set for 8months befor it was ever started up, so do i need to do the rings again?i cant bore them again as they are 1mm pistons could it just be the rubber rings that go around the top of the pistons on the cylinder???im just glad both pistons and rings are hole

 

[kustomkarl]

Is there any scoring to the cylinders? you might be able to pull the cylinders off and run a hone through it again and either throw on a new set of rings or try using the old ones if they are in good shape, and the end gap is within spec.

Karl

 

[irish88]

yep my cylinders look like brand new so do the pistons

 

[mudpie]

rings could be stuck with old sticky fuel or rust
add some penatrating oil and let soak
re-do your compression check
make sure you clear out the oil before compression check
good luck
mud

 

[irish88]

with oil in the cylinders a` (wet test) i get 110 psi maybe i put the rings in upside down?

 

[kustomkarl]

There is a pin on the piston and the end of the rings have a L shaped cut in them at the free end gap to fit it just right...they won't compress if you have them in upside down. Your compression should be 150 psi...

Karl

 

[irish88]

just took the jugs off and everything looks good rings jugs pistons it all looks good the hole on the side of the piston should face away from the exhaust right? i must just need new rings even tho they all look good

 

[seadoosnipe]

Measurements...

just took the jugs off and everything looks good rings jugs pistons it all looks good the hole on the side of the piston should face away from the exhaust right? i must just need new rings even tho they all look good

Since you have it down, you might have the jugs measured as PWCjunkie stated, to see if they are within tolerances.

You said your one bore oversize. That makes your bore now 82.25 mm or 3.238". So, get them mic'd, see what you come up with. The possibility that the original work was over the limits, is possible.

 

[irish88]

i had them bored 1mm sent the juge in to full bore ill try to mike out my jugs today thanks for all the help