Re: How would 4hp perform?
It's going to be good. A TC with stock springs will engage at 2200rpm and shift/ hold your engine around 3300. I have 3.5hp and tried many different transmissions. I tried messing with the TC springs and stuff, see my thread "speed acceleration not satisfied". The TC is kind of weird in that you don't hear the engine rev as you accelerate, but you do hear a slight whooooooooshhhhh as it shifts up.
If you are willing to tweak or adjust the governor I would suggest you you go with a single speed centrifugal or disc clutch, as the acceleration isn't so good but the response is much more predictable, smoother, and sounds right with the revving. Also, you won't be losing performance as time goes on due to belt wear.
The cvt works great if you keep the engine in the original rpm specs, but when you open it up to find your powerband from 3000 to 5500, the cvt becomes extremely disappointing. It really only makes use of 1000rpm of powerband for smaller hp motors, and you can decide where it starts. I adjusted mine to engage at 3300, it shifted around 4100 and the low speed drivability was much worse. If you find a way to get the TC to make use of at least 2000 rpm of powerband LMK.
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