2001 yz300 big bore issues!

Jul 24, 2018
I have a 2001 yz250 i purchased a big bore kit from millennium technologies so I have a replated cylinder, and all new gaskets entire top end was redone! As for the bottom end I rebuilt the transmission but left the crank and seals alone. When starting this bike it backfires every now and then and in 1st 2nd and 3rd doesn't really like hitting powerband it sounds like a v8 truck bouncing off a rev limiter I have timed the bike multiple times. I have jetted the bike a 100 times. The bike runs awesome on the low end tons of torque picks the front tire right off the ground but I'm having issues on the top end of rpm any help would be awesome thank you!