1995 GTS blown front piston

[Yam00Star]

Hey Everyone! I’m new to the forum and a new SeaDoo restorer. I purchased this 1995 GTS with a 587 single carb last summer. When I checked the compression, using a Harbor Freight tester, I got 90 in both cylinders. After looking into these testers I realize it was a bad idea. I still got it to start out of the water on a hose and in the water. It would crank a long time but start. I took it out on the water about a month ago. Ultimately it died on me. When I got home I checked the compression again with the HF tester. I got 90 on PTO side and 0 on the mag side. Pulled the head and found the mag side has a hole at the pin for the rings. (See Pictures).
Questions: what causes this type of failure? Will a top end be adequate or should I go deeper? How much over would take out the scoring? I noticed the scoring is now rusting?
Any and all advice would be greatly appreciated.

 

[Stevie96xp]

Most likely an oil line broke and cause it or not be lubed. Hopefully the crank survived it if so new top end an good to go

 

[burtshaver2021]

I can’t see the scoring, take it to your machine shop, they will measure it and let you know what size over to order, probably .5mm oversized

 

[Yam00Star]

Most likely an oil line broke and cause it or not be lubed. Hopefully the crank survived it if so new top end an good to go

Thanks. I’m suspect of the oil pump too. Not much smoke, I’ll be premixing until I get that figured out.

 

[Yam00Star]

I can’t see the scoring, take it to your machine shop, they will measure it and let you know what size over to order, probably .5mm oversized

Thanks, I’ll update when I find out more info.

 

[Stevie96xp]

Thanks. I’m suspect of the oil pump too. Not much smoke, I’ll be premixing until I get that figured out.

The pumps are super reliable it’s the lines that fails. I would not premix it not ideal. It uses more oil

 

[mikidymac]

Looks like it ran lean. Typically from fuel system/carbs that have not been maintained.

 

[Yam00Star]

Thank you! This is exactly what I needed to know. I rebuilt the carb but that only means it worked. It doesn’t mean I had it set right. I will figure that out before I start running it. Thanks again, I really appreciate the advice.

 

[nibroc]

ya got that GTS runnin yet?

 

[Yam00Star]

ya got that GTS runnin yet?

Not yet. I got it back together. It turns over by hand nicely. The starter wouldn’t turn it over. I pulled and rebuilt the starter. Still same problem. Switched batteries. Now it only turns over with the plugs out. I’m thinking the starter is wore out.