"Oil overflow" huh? where is this oil coming from?
If would say if oil is dripping from your filters thats not a good sign
Maybe be a little more specific.....
Who ported your bike? Your builder should be able to get you really damn close.
I have an aggresive dune port and I'm running 310 mains. And thats with Cpi pipes.
Maybe your "340" main is too big, when you hit the gas your shee chokes on fuel. Just taking a guess.
If you have all your major bolt ons like, pipes, reeds, cool head, timing plate..etc. You can get it ported and will make a huge differance. I had Brandon @ Wildcard Racing do mine and he is a site sponsor on here
What is you jetting right now? Stock carbs?
I'm at about 5200ft here.
My buddy with close mods to yours runs 270-290 mains, needle on middle clip, stock pilot. Stock carbs. Thats for about 90 degree weather.