Just run LO206, there is something about that class that is too much fun!!! Hard to describe, but we have ran many different classes and engine packages through the years, and LO206 is so much fun, with out all the stress of engine/clutch tuning etc. Just set up your correct gear ratio, put gas and go.
It is so cheap to run, all you gotta do is change the motor oil every race weekend, they use cheap pump gas.
TAG, Yamaha KT100 can get pretty expensive with rebuilds every 3 to 4 races if you wanna stay competitive, new clutches are around $365, plus you have to run race fuel and pre mix every race, ad another $95 to $105.
Just do LO206 for a season or 2 till you get real good at it, then switch to whatever engine you want.