426 overheating Badly

Here's my scenario, I have the engine in a quad frame for MX.

I have a 42 pilot

172 Main

Needle is on the 3rd clip (stock needle)

It's ported, K&N filter, 13:1 piston, 450 cam mod.

Wet sump kit

It has no response off the bottom end, but screams once it is wound it, but takes a while to get there. I just checked out all the jetting guides and printed them out to try some different combos.

My plug is burning kind of a grayish brown, and my exhaust tip is a little white, so she was running lean.

When I come off the track the coolant is down to the fins in the top of the rad, and she is blowing steam furiously.

I installed a catch bottle, and a high pressure radiator cap.

I figured since it was running like that I may have a leaky head gasket, so a new one is on the way, and there was a minute amount of drip from my weep hole, so I ordered a new mechanical seal.

I am going to try all of this, and run the jetting I was running before.

But if anyone else has any insight, I would greatly appreciate it.

First, confirm that the flywheel key is intact by checking actual TDC through the spark plug hole against the timing marks. Then check the cam timing.

I've got the whole head off right now still, I am gonna check all the timing and whatnot in reference to the YZ450 cam mod thread. I bought the engine used, so something could be out of line. What should I check for when checking the flywheel? Thanks for the info.

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