Well, I may not have heads and a cam, but I do run a Zex 125 shot in the summer and jet it down to a 75 shot in the winter [ cold pavement= poor traction].
Been almost two years now, and 23 re-fills on a stock tranny.
So far so good.

 

I have been doing it for a year. Been to the track, roll raced and manually shifted it a few times and it is doing great.