to replace the stock variator by a 'racing type' variator is always a gain in performance with a minarelli engine.
those stock vario's are worth s**t, it costs a lot of work to tune them and then stil overrev the engine @ max speed.
i mostly use variators that are designed to be used with a 70cc cilinder like malossi, Doppler, polini...
i prefer the Doppler, it's cheap, uses big rollers(19X15.5) and is very very easy to tune and compared to a stock vario it doesn't overrev @ the same speed with the stock variator and exact same wheigts...
+ ik noticed a gain of +-7mph compared to stock with my stock 50cc cilinder.
it even doesn't overrev the engine even with 24gr @ topspeed(!!)
the range of those vario's is much wider then the stock, period.
and if you can affort it try a torque driver from polini/malossi/doppler also, this in combination with a race vario is just super, no strange dips and again even much easyer to tune !:winner: