How can I tell if I need a new cylinder or a new piston/rings?

[nick614]

I was trying to figure out why my seadoo 94 spx would not start and I found that my compression was 150 in the Mag cylinder and 25 on the PTO cylinder. I did notice some scoring in the cylinder with the bad compression, but it would still crank over. This seemed to happen when a oil injection lome broke and I was not aware.

How can I tell if I just need a new piston and rings?

If I have to bore it out and insert a oversized piston can I just do one cylinder and leave the other alone for now?

I still have to take apart the cylinder a little farther and check out the crank and bearings.

I have attached some pictures.

 

[kustomkarl]

I would pull the cylinder and have a shop check it for wear. It is hard to tell from the picture how bad the cylinder and rings could be. The crank and or bearings could be damaged too but can't tell till the top end is removed. if you bore out 1 cylinder you have to do both to be equal in size. you mighe lucky and only need a piston and rings for the one cylinder...get it honed if not scored too bad, add a base gasket and head "o" ring and done. Have it checked and go from there.

Karl