I don't know about the carb specs but an easy way to gain a little more clearance is drill the mounting holes for the rear skid down a bit. try about a half an inch then rivet on a sopport plate to make sure it stays there.
Clutching is the easiest and best mod to make. Even just cleaning and replacing springs once in a while keeps performance up.
i wouldnt worry much about jetting. as for suspension there is not really much you can do there. if you want some sort of gain with out clutching then mabe you should look at a track.
