If you've got rain to contend with, (at least on a regular basis) all the extra torque of the GXH50 is going to spin the spindle against the wet tire...
Most of the feedback I've seen on FD versus equivalent chain drives, is the power is about the same. (FD has extra 'rolling friction' caused by spindle deflecting the tire., Chain drive is very efficient from sprocket to sprocket; losses in gearbox are about the same as rolling friction of friction drive)
However, Staton's chain drive (including his Nuvinci drive) has a freewheel, so you can coast downhill, and not be pushing the motor.
A CVT allows you to maximize the power output from the engine; so you'll definitely be able to go uphill faster than you would with a fixed ratio of the same engine. Peak power output of the 35cc Honda/RS engines are about 5500 RPM, with Max RPM pushing 8000 RPM. The CVT allows you to keep the engine RPMs in the middle the peak output band when hill climbing or when on the flat.
I have the same issue with my FD Mitsubishi (which has a max power RPM which is much closer to the MAX RPM) on hills. What happens is that, as the engine slows down when climbing, being a fixed ratio, the engine RPM goes down as well. As the engine RPM slips out of the max power RPM, power output gets less, causing speed to drop even more, causing speed to drop, causing RPM to slip further away from max power band ... and so on.
With the CVT, you just slip the ratio (equivalent to shifting to a lower gear) up a bit, and you can keep the motor at max power - you'll end up going a lot faster up the hill than you could with a fixed ratio drive.
I would like a Nuvinci system; even though I haven't owned one. I can tell you this; the folks who have the Nuvinci are very happy with it...
Take a look at the Nuvinci threads in the CVT forum... In particular, take a look at the discussion in sparky's
Nuvinci poll to see what the folks who actually own a Nuvinci say about it.
The other point that the folks who own a Nuvinci bring up, is that they're able to run their engines at a lower RPM when cruising, which can't help but improve engine longevity and mileage.
Now, you don't get anything for free. There is a loss in POTENTIAL top end, as a Nuvinci is somewhat less efficient than a fixed gear system. But, a fixed gear system is virtually
never geared for maximum top end. It is a compromise gear ratio, that gives you acceptable performance at lower speeds, with (on Staton 'standard' systems) max RPM at about 30 MPH.
This means that at 30 MPH, on a fixed gear system your engine is screaming, and max torque output (at 5500 RPM) occurs at about 21 MPH.
HOWEVER
According to calcs using
bikepower, a 180 pound rider, on a 50 pound bike/drive, could just about maintain 21MPH with 1.4 HP on a 6 percent slope (6 feet rise over 100 feet horizontal run,) with a 75 percent efficient drive.
If the slope is anything steeper than this (which is the max recommended slope for freeways,) then a 35cc motor is going to bog down. And, you because your power output is in a relatively narrow power band, you're going to not be able to handle a much steeper slope.
But, with a CVT, you can raise the ratio at will. Say that the slope goes to 10%. You would just raise the ratio until you maintain a speed at 5500 RPM and keep cruising. According to
bikepower, that would be between 15 and 16 MPH for the same power output as 21MPH at 6%.
The one accessory I think you would
really want to have on a Nuvinci system would be a Tach.