there are absolutely no rules to engine modification, just no aluminum flywheel
That is not a good set of rules!
These flywheels will not hold up used like that , and when they come apart it is ugly! We started out with a "no billet" class, after a season I cryo'd a couple of our wheels and it scared me! We were close to disaster!!
As for power from a 12 hp flatty, they can make enough to be more than a beginner wants! And V-twins can be built to be down right dangerous with the wrong person on them!
Read through the builds and you will find about everything you need to know.
EC Carbs, ARC, small engine cams...just a few of the suppliers in engine parts.
But again, PLEASE, if your not going to put a billet wheel on those engines, do not get crazy with the builds. I would hate to see your daughter or you get hurt.