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.