was looking at my pistons tonight and i see that the one that i just had the cylinder replated looks black. i was looking in the exhaust post and the piston is black on the exhaust side and the top of the piston is clean.? what do you think this could be. not sure if i have antifreeze leaking in there?.. also when the engine went down last year the head got a little chewed a bit as a screw went up and bounced around the top of the piston and head. now the marks are just in the combustion chamber would this have any affect? i have ran heads like this on cats with no problems at all but thought i would ask to see if there are any other complications as detonation.

Are you 100% sure that cylinder is firing? No carbon on top and some on the exhaust sounds to me like it is not firing or at least not all of the time.

yeah well thats what i was thinking as the plug was soaked but was just thinking if antifreeze burning thru would give the same affect?

If it was a small leak, the cylinder would or should I say should still fire. It would look some what the same but usually the plug would be clean and dry(lean looking) with a funky color. You would also have scoring on the skirts(minimal lube). If it was a major leak, you should see antifreeze and that piston should be permanently fixed to the cylinder. :ohmy: :cussing:

Mach69, are you saying that the top of the piston is completly clean? If it is, then it is running too rich and is an easy fix for you. My 99 Mach Z stock was too rich with the stock pilot jets and it would foul plugs and keep the tops of the pistons looking like they just came out of the box. Once I rejetted with 45 pilots I got the top of the piston to be mostly black with some washed off, perfect piston wash. The benefit is the plugs stopped fouling too. If I can be of any help, e-mail me at spkrdctr@aol.com

well no i know that is it very rich as it was running oil in the tank and oil injection so. then the top of the piston was clean and i know that this is rich. but my real question was the side of the piston the exhaust side was black? and question #2 is will the head having been hit several times have any effect?... in the head it is only a combustion chamber. my concern is would this have like a detonation effect?... and what was the black on the skirt?... is this just a rich effect ?

Mach 69, that discoloration is normal as your running so rich. If your piston top is clean, then your motor is very safe. If it is running good at all, you can drop the jetting one jet size at a time until you get dsme black on that piston top. Once 80% of the piston top is black, then you are pretty much ready to go for all weather and trail conditions. Also, try running the NGK Gold Palladium plugs (EV Series) as they seem to work very well for me. They are premium plugs without the premium price.

Your head should be fine as long as there are no sharp or pointed edges. Dents are fine but peaks in the heads will cause detonation.

I just lost the headgasket on my wildcat AGAIN. This time it took out the piston. I'll have a couple pics soon and show you what happens to a piston when coolant drips on it. Looks like the surface of the moon. Little craters. I had no scoring on the piston skirt. The coolant was burning away, and I noticed a major lose of performance.

The black piston sounds like some sort of blow-by or it got really hot at some point. I had black marks on exhaust side of the pistons on my RZ350 bike. I'm pretty sure that it was caused by heat.


PS. Can you PM me a good carb set up for a 700 Wildcat (40mm carbs, gutted airbox, and stock twin pipes). You have some experience with this engine don't you???

yup i do ill send you some .