If it's a 150cc with a CVT Trani, then pretty much all you can do is Lower your gear ratio in the gear box it self. Use a bigger sprocket on your axle, to lower your gear ratio. Or the reverse on your drive train sprocket.
Smaller tires will give you lower end. And lighter Rollers or sliders, will keep your gear ratio lower, for longer amount of time, so not losing power, as your climbing.
You can also put in a lower grunt cam it in, I believe that would help also.
But not sure what you consider hill climbing. That definition can very a great deal.
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