[charleswrivers]

The cam will make a difference. I can't speak forgoing big bore as I'm still running 150cc, but it should. I was given the recommendation when I needed to do my rings from.some smoking that, since I wasnt looking to spend a lot, to just do rings/piston assuming my cylinder was good and do a cam. That's all I did to great effect.

Going bigger carb will generally lose low end slightly to gain high end slightly, more flow at a lower velocity. Again, I'd verify you're not lean running the 125. It may help if you have more displacement but 24mm seems fine for 150cc. The head work would probably make the most difference, from all I've read.

Those must be some big hills... Ive got some big retention pond hills around and mine will just chug up them w/no problems and zoom up them if I goose the throttle. For the money, I'd still check your jetting, go with an A12 and maybe step down a gram or two in your rollers. Running a larger sprocket will lower your gearing as well and provide an instant improvement in torque while sacrificing some top speed. I've run 500+ lbs between people and cargo and it struggled and had to be revved out a bit and struggled up some moderate hills. Done the same running around weight-wise post new piston/rings, belt and cam and it was easy going. I have to believe it's mostly cam w/a small bump from higher compression. I can do what I did before without having to really rev out the motor.

Does your engine seem to running right otherwise?