Quote:
Originally Posted by RacinNinja
Almost a complete hole.....this is from our bike with the Powroll kit. It's a second hand piston we got...crown was way too thin after we looked at it more in depth and it had been machined underneath the dome around the pin bosses creating a weak spot. Didn't find out until it lost power during a race and started missing. I killed it and pulled off the track....just in time before it fully grenaded.
You said there was a lot of carbon on the rest of the piston...running rich can cause this to build up, create a hot spot and cause detonation. Running lean can cause detonation too as well as ignition timing, cam timing and other things.
Although, in this case, I suspect you ran out of coolant, overheated the motor and this is what caused the cylinder temp to rise and detonation to occur.
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The piston tops are clean, the carbon buildup in in the top 1/8" of the cylinder on the left side, and on the valve heads on the inside of the combustion chamber. I will clean the carbon off of the cylinder and probbably hone it, and I might try to polish the combustion chamber, I decided not to because I didn't want to lower the compression, but I want to prevent carbon buildup. If i decide to do a high compression build I will forsure polish the combustion chamber, but I might decide to buy a stock kawasaki piston just for my trip, and go high compression when I get a little more spending money.