PUT A 34MM BORED OUT TO 35.5 WITH UFO PUT A 220 MAIN TRYED 210 STARTS FINE. MID TO UPPER RANGE FLATENS OUT ..... NEED HELP PLEASE ...............................................

 

buy a yamaha!

 

oops i have po pos, i like yamys

 

If I understand what you mean by flaten out, I would say you are lean. Go richer on the main one step and see if that helps. You could grab the choke when it's acting up and see if it gets better or worse. If it gets worse, you are rich, and if gets better, then you are obviously lean. Running rich typically gives you a sputtering sound and it sounds like the engine just cannot gain much RPM. Lean is more of an 'empty' feeling, like when you forget to turn the gas on and you are under heavy load and the egine just flattens out and dies.

 

I can tell you that with the mods that you have you are running to rich. I also have a 34mm bored to 35mm with a 210. I also have it ported,bored and milled head. It runs perfect. Plug is nice and milky brown. Your motor wont breath as much so you need to go smaller on the main jet. Try a 190-195 main with the needle in the top slot. dont worry it wont run lean on this setup. I used to run it like that untill I got my motor ported,bored,and milled then I had to go bigger.