Group k sleeper 787 piston scoring

[kenneth.mccoy1]

I have a 1997 seadoo spx with a group k sleeper kit I recently installed. I got a little paranoid about making sure everything was good so I popped the rear cylinder rave valve off and it looks like part of the piston is scored. It only runs about 1.5 cm down the piston from the top, I can’t tell if it’s something I need to worry about or not. I poked the lower ring and it isn’t Locked in the piston, it moves in and out. The thing runs great, I topped out at 60.2 this morning. I’ve got 150 psi in mag cylinder and 145-147 in the pto. I was running premix at 40:1 but after seeing the scoring I premixed it to 32:1. About two and a half hours on the engine, new crank, new pistons, both wsm. I’m just putting down the information for reference. Thank you all. I’m also running XD100 oil full synthetic

 

[mikidymac]

That doesn't look good and isn't normal.
Call Group K and send them pictures, they are the best.

 

[kenneth.mccoy1]

Will do, thank you.

 

[kenneth.mccoy1]

Talked to Groupk, he recommended I sand the scoring off the piston and or cylinder wall and pressure test for air leaks which I did not do the first time. Rookie mistake on my part.

 

[kenneth.mccoy1]

Took the engine out and took the head off, this is only my third engine rebuild so I’m not sure what happened but it looks like it got too hot and melted some of it

 

[etemplet]

I'd check the ports to make sure they have a chamfer. You may have a carb issue. Good Luck with it.

 

[kenneth.mccoy1]

All of the ports were chambered, but I had an air leak on the left side of the rotary cover. I sent Groupk lots of pictures, but I think I’m gonna need a new piston lol.

 

[burtshaver2021]

Rookie here myself, I’m interested to see what others think but if I had to guess I would guess that it’s running lean, either fuel deprived or an air leak either at the carb base or the crank seal. Did you rebuild the carbs with Mikuni? I think you mentioned it but did you do a leak down test before and after you rebuilt the top end? How did the machine idle? And what did the plugs look like?

 

[mikidymac]

New piston is needed.
It is strange that the piston is eroded at the ring grove.
Always pressure test an engine and service the fuel system.