im helping a buddy rebuild the top end on his get ski. we get the top end off, and find that one piston is chewed to ****...the other looks perfect.

what would cause 1 piston to detonate so badly and the other to look perfect? my first guess was a faulty injector but this is my first tear down with a 2 stroke engine. anyone know what's up? i would hate to rebuild this thing and it fail in the first 5 miles of riding.

 

could be a number of things , lean knock from partial blockage in the fuel delivery , maybe something small like a spark plug electrode got broken off and it made some minor dings and looked liked detonation . swap injectors would be a good start. is there anyway one cylinder may see more heat than the other?

 

the plug to that cylinder looked good. strap was there. intake and exhaust look like they are very evenly distributed between the cylinders. i think im going to tell him to send his injectors out to be tested just to be on the safe side.

oh, the lower ring was cracked in a few places, and the upper ring was welded into the piston. sounds like at this point we are looking at the injector huh? hopefully we find something wrong with it.

 

Is the ski oil injected? My 1978 yamaha eudro 250 lost power & wouldn't start. Come to find out the the oil line that feeds the engine the 2 stroke oil had collapse. When I pulled the head it looked just like what your saying.

 

Is it a DI seadoo? May be a faulty injector as mentioned, check your oil lines, and lastly a DI doesn't need a reason to fail....lol I have one in the shop now that we put an SBT shortblock in and it has all of 4 hrs, now it is seizing up after about 30 seconds of running.