Compression

[biggiescott]

What is an Acceptable compression range for a 1995 sea-doo 650 gtx with a 1mm over bore? I'm measuring 125psi on both cylinders

 

[Whus02]

150-155psi is perfect, below 135psi is time for a rebuild. If the engine runs fine in the water, then you might want to try a different gauge.

 

[POPPS]

If it starts well, runs well, and the plugs look like a light ale, ( after running, and not after a plug chop)...then 02 is right, try a different gauge.

 

[biggiescott]

It’s probably the gauge.
I just finished putting the motor back together with new crankshaft all new gaskets, new top end, cylinders were recently bored etc.

 

[gazzaskirepair]

Have you got the piston rings in the correct way round ? The markings on them facing up

 

[chipskittles]

I'm waiting on a new gauge myself, my boat runs ok in the water but the starboard has always had a tendency to stall at low revs. I think the last compression tests I did with my old junk gauge were barely 100 for that motor and 120 or so for the other motor so I suspect starboard needs work anyway.

 

[biggiescott]

Have you got the piston rings in the correct way round ? The markings on them facing up

I have the bottom rings with markings on top and top ring is cupped I was told the cupped part faces up and on those rings the markings are on the bottom

 

[gazzaskirepair]

That’s correct you must have a RIK rings they have markings on the bottom of top ring
Maybe try another gauge

 

[chipskittles]

I'm waiting on a new gauge myself, my boat runs ok in the water but the starboard has always had a tendency to stall at low revs. I think the last compression tests I did with my old junk gauge were barely 100 for that motor and 120 or so for the other motor so I suspect starboard needs work anyway.

A new or quality gauge can make all the difference. Both of my motors have 145-150 with a vintage Peerless compression tester, what a difference!

 

[mikidymac]

I have only seen rings with the marks facing up. Used a lot of RIK (WSM) ones over the years.

Typically if you have the tapered ring upside down or in the wrong groove they will not fit into the piston groove correctly.

 

[biggiescott]

I have only seen rings with the marks facing up. Used a lot of RIK (WSM) ones over the years.

Typically if you have the tapered ring upside down or in the wrong groove they will not fit into the piston groove correctly.

I have wsm rings installed and I have a set of sbt unopened and wsm markings are on bottom of top ring and on sbt rings the markings are on top of top ring. I’m pretty confident the rings are in properly. I’ll try a better gauge and make sure I crank until it stops building and go from there. Thank you everyone for the help.

 

[mikidymac]

I have wsm rings installed and I have a set of sbt unopened and wsm markings are on bottom of top ring and on sbt rings the markings are on top of top ring. I’m pretty confident the rings are in properly. I’ll try a better gauge and make sure I crank until it stops building and go from there. Thank you everyone for the help.

I believe you, just can't say I have seen that. Let's see what the new compression test says.

 

[biggiescott]

I rechecked compression tonight and front cylinder is 145 and rear cylinder is 142 not quite 145

 

[chipskittles]

Doesn't seem that compression will be your issue