The Blockzilla would run right with that 550 Rotax most of the time. The only problem is he didn't know much about the acohol engines when it comes to mainanance. He never drained his carb after a race and never wd40'd his engine before winter, so all that acohol set in that engine and carb all winter long and basicly ate everything up so it didn't last long this season. He's rebuilding though, and the 550 guy just bought a 600+ Rotax. Now if they could just get them down to 3-400 lbs.