I am not 100% sure this is the reason because it could have been my poor tuning also....

I have a NSR12S3 and it started getting hot 2 weekends ago, It was around 190-170 range for probably the end of two heats, I was also very low on gas but still a little left in the tank. I started richening it up and it ended up getting cooler but I was wondering why it would have to be so rich..? So I ended up trying a O.S. P6 Turbo glow plug instead of the RB 7 turbo plug that I was running. It made the motor cooling by lowering the compression I believe, So another thing I noticed is the carbon buildup in the exhaust port and the top of the piston, would a little carbon on the piston raise the compression eneough to make the motor run hotter? In the go karts I raced a little carbon on the top of your piston was a good thing. I was wondering this because it seems the standard plug to run is a 7 turbo plug.

When The motor started getting hot (which is now resolved with the O.S. P6 turbo plug) it was probably 85-90 degrees out side and 35-40% humidity here in Nebraska.
I just noticed today that on Josh Cyruls website he said on the Nitro motor maintinence that you should clean the carbon off of the top of your piston if you run a castor based oil (or something like that... ). Could this be the reason why? The motor mekas great power with the P^ plug though dont get me wrong....