Re: Increase 7.5 hp
put on a Tillotson HR series from EJ creations modified for methanol, re-shape your exhaustd ports to "D" shape, Skim the head to get about .036" squish, make some reeds from .018" thick G-10 epoxy-glass and bend open the stops, open up the holes under the reeds as much as possible, run 5% nitro, 10% castor, 85% methanol, use a racing prop, and hang on!!!
Seriuosely however , there is little other than the racing mods mentioned above plus the correct prop, and a tune up which will give you any more power. On neglected engines, a de-carb and tune up can often give you a 20% boost in power.
