Hole in piston.....xl 1200

[scott71]

I recently purchased a 2000 xl 1200 ltd which came with a new yamaha crate motor. I before installing the motor I installed a block off kit, d-plate, and riva air cleaners. I pre mixed my fuel at 32:1 with amsoil interceptor, I babied the engine for the first 1/2 of tank of fuel and engine had a tendency to just die while running across the water. No warning signs of any kind came on and engine started right back up. I went back out today to finish off the other half of tank and while riding engine lost power and died..Towed back to shore and brought it home. Removed head and found that the rear piston had a hole in center and melted down around edge, it looked like it was not recieving any oil. center piston has slight melting on edge very low compression on cyl. Front piston is fine with excellent compression and plenty of lube on cyl walls. I have built and broken in several engines, so I have some experience at proper break in. Is it possible for engine to have been sucking in air and running to lean? Water was coming out of my pilot tubes on the sides of the ski, so the cooling system appeared to be working ok. Any ideas as to what might have caused this? I guess the big question is that the crank appears to be ok and I would like to replace the top end with an exchange kit, how can I tell if the crank recieved any damage. Motor turns over completely and smooth when I applied oil to the rear cylinder. If I rebuild or replace the engine I do not want this to happen again. Are there settings on the carbs to richen or lean if you premix as I did? Any help would be great.. Thanks scott

[Phil STX15F]

Re: Hole in piston.....xl 1200

If your piston has a hole in the center of it that means you have detnation. You will need to rebuild the carbs, because you have a pluged up carb that is causing your problem. Do you have any idea what took out your first engine? Was it the same type of failure?

[Technical Support]

Re: Hole in piston.....xl 1200

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