moto_ohm

Hi all new to the forum. Im in need of some advice, i recently brought a Beta Rev 3 2001. The bike is great, starts easy and runs ok, the only problem is it feels a little underpower and doesnt rev cleanly compared to my mates Techno and Sherco. I have had a look at the timing plate and it is in the middle of the adjustment! i removed the air filter (which is clean) and it improved (not 100% but better) this is making me think jetting. I have 150 main and 30 idle. The bike has loads of compression, sometimes it kicks back (is this normal? was thinking over advanced) Can anyone shed any light?? Cheers