I would be very leary about putting a larger carb on the motor that you have now. A rule of thumb is that the larger carb will give you more top end, but losing a litttle bit of torque and responce down low. The smaller carb will give better torque and responce down low, but limit your top end. Right now I am running a 170cc BBK, PnP Big valve Head, A12 Cam (got from Tom), Uni Filter, Custom Exhaust with a modified TTR125 muffler, 10G rollers, 1500 Contra Spring, 2000 Clutch Springs. I am still running the stock carb though.
I built this engine to be as bullet proof and as user friendly as possible. When we go camping, approx. 10 or so familys go (mostly dirt bikes). I wanted a motor that could handle kids learning how to drive and just be sort of a who ever wants to drive it buggy (i did fab up a throttle limiter).
In testing it I have put the buggy in some pretty wierd situations, climbing hills without a running start. Driving down into canals (dry) stopping at the bottom, then climbing out from a dead stop. I tried to copy what a new driver or one less experienced might do to the buggy. It passed all of these tests with my 220lb carcass and my 12 year old son aboard. Also, it is still faster then the suspension can handle in the rough stuff.
I would highly recommend the A12 cam for good power in all a round driving conditions. However, I can only speak for the cam that I got from Tom. I have a suspision that not all cam makers use the same grind or quality.
Almost forgot, this engine is in a 2005 HH150. The other mods that I have done is to add "real" 4-point belts (3" lap, 2" shoulder), a passanger grab bar near the dash and Yamaha Blaster shocks on the rear (big improvement).
Good luck and happy motoring
