I recently bought an 06 250X with the following motor work done to it:
08 R cam/head
Wossner 13.5:1 piston
"Special" carb tune by Eddie Cruz Racing in Long Beach CA
4"x4" cutout on top of airbox, top triangle cutout on left side
Twin-air air filter
Stock header, FMF Q4 pipe w/ spark arrestor
The jet/needle set up is as follows:
172 main
42 pilot
68 leak
NCYS needle, clip in 6th position down from top
The bike starts and runs fine, but the idle is high and I notice slight bog at lower RPM (nothing severe). I ride at 4000'-8000'.
Now to the problem. I recently pulled the plug to check it, and found it was wet and black, lots of carbon buildup on it. I also peeked down into the cylinder, and the face of the piston looks the same way, dark black flaky buildup that looks wet. It does not burn oil or smoke, and after some research it seems like this carb set up is very rich for my altitude. Will an overly rich mixture produce these types of buildups? What about an overly oiled air filter?
I am going to do a compression/leak down test as soon as I can pick up a gauge. If the leak down test indicates blow by or bad valve seals/guides, that will answer my question, but I'm wondering if mixture could do this too. Any help is appreciated.