are you still running the standard main jet ? stock is a #200, and the optional is a #210
each size jet up will be in 10 increments, i would buy the next 2 jets up, from what you have now
i can get the jets if you need them, this shop is 5 minutes away from my place, then post them over to you if you need.
they also sell on ebay too.
one jet will cost you about $12, or cheaper for 2, about $16 the pair
yours look like this one, 4/042 in the middle of the page.
http://showandgo.com.au/
i had my IT200 bored out to the 2nd o/s last year, and replaced my piston/rings etc etc
i had to rejet the carby to suit, i ended up going to a bigger pilot (a #60) and the main needed a #360,
the standard jetting in the VM34SS was 55/340 though, but since i fitted the Carbon Fibre reeds, and have a performance muffler it was running a bit lean.
and i'm using a Unifilter in the airbox (has a modified/twice as big as std, intake lid on it)
i found another basic spec list for you too, good point of referance-
http://georgiaoffroad.com/dirtbike.php?modelid=1122
together with the other mods,
it has made the throttle more responsive, gave my bike a bike more torque off the line, and also lets the engine rev a little more
for the $30 odd dollars they cost it is a worthwhile mod.