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[Avery934]

Can anyone tell me what could of caused this piston to end up like this? It's the back piston out of a GP1200 with the oil injection still on. The other 2 cylinders had 120psi. My guess is failure from the oil injection. Picked this ski up from a dealer that was going out of business for 250 bucks

 

[Quinc]

Might want to get an oil block off kit and run premix. Looks like an air leak issue though.

 

[All stock 701]

Did you check to make sure that all of the oil lines were still attached to both sides?

 

[Freakie]

check if that carb is flowing fuel properly....looks like it ran very lean and melted a hole in the piston.

 

[Avery934]

All the oil lines were hooked up. When the shop took the ski in on trade back in 06 the tech said it checked out fine. It sat for some time then when they sold it all of a sudden it had a no compression in back cylinder. Where would it be leaking air? And could a dirty carb cause this problem? Oil block off kit is already in the plan. Just don't want to do tokens and have this happen again. Thanks for the advice! Hope everyone has a great day!

 

[Freakie]

if the carb jets were blocked, just gunked up, or fuel pump diaphram went faulty (hard or holed) or it was not getting an air pulse from the crank case....thats enough to blow that hole in the piston. open it up and check every possible part, replace most and blow all orifices out with compressed air

 

[Vumad]

Im no expet but looks like a lot of heat on the exhaust side. I would think thag if it were the oil pump that it would have more damage on all sides and a little less heat. Air leak sounds like a good suspecion but running lean from a dity carb sounds like a much easier explination.

 

[Dartman]

the gp1200 has inherent fuel pump internal round disk valves that go bad and cause weak fuel pump pressure problems and blowup as shown
dont know the cause
but they all do it
replace them annually
gp 1200 have 3 stock sbn pumps on them
before on the 1100 used external pumps and didn't have this issue