70cc(45mm) alukit,high comp head, carbon reeds, weekends intake, techno circuit pipe, vm22 carb(17.5 pilot/ 75 main), k&n filter, 52:1 premix. Having problems with the bike backfiring after it shifts in 2nd gear and get about half throttle. If you go past half throttle it wants to bog pretty bad, but is very responsive up to that point. If I'm thinking correctly would the timing be off if it is backfiring like that? Also not sure what carb adjustments to make from this point to fix the bogging with the throttle at halfway. 2nd question, I've never had a 2 stroke that is this hard to start. You have to spray starting fluid in it everyday to start it and once it warms up its fine until the engine is cold again then you have to spray it again, any ideas? (edited)