first:
mfgsupply.com sells spare parts for your series 20 unit..
so in case something's broken/worn and needs to be replaced..
you know where to look
the sliding hub can get a bit chewed up, remove it from the moveable sheave,
remove all burrs (from it and the moveable sheave it sits in) and try again.
Well, the series 30 is NOT a successor of the series 20
Comet made both at the same time as successors to the TC88 [sym] and cat99 [asym] series
which are merely identical apart from the narrower belt.
symmetric systems generally have less wear on the belt and thus a slightly higher efficiency..
the series 30 has the benefit of easier self containment (using a backplate) and the aforementioned overdrive capability with the smaller driven unit.
One is not better than the other, they're just different...
According to Jim Donovan only the symmetric ones are made for go karts really, the series 30 is only meant for mini bikes.
IDK if I can agree with that entirely...
I (as most) like the overdrive idea and the ease using the backplate on karts that previously just had a clutch and not to forget the cheap chinese ebay clones that are almost as cheap as cent clutch.
And if one's willing to pay for that with belt wear... IMHO that's still a valid option.
What I think is true is that the series 20 was MEANT for karts and the series 30 was MEANT for mini bikes
frankly.. if you don't run a much higher power engine, stick with the series 20!
if you upgrade your engine (not mod, replace!) you should upgrade to a series 40 tc.
the series 30 is easily available but just a PITA to mount properly on your kart,
and the gain might not be worth it.
'sid