Oh man, you’re gonna smoke them. Literally. LOL. These spec motors have excellent porting out the box. Even running on gas they’re still 30 HP motors. For your motor Hegar sells a belt driver hub, too. I’d go that route, get the cheap BMI jackshaft and a 3 disk gator. You can probably keep the carb on it now and run a 100cc reed pipe like a Q98/CRE6/S4.