I had a modded dt50 motor stroked out to 72cc then flywheel completly removed and replaced with a 1/4 oz aluminum plate with a slot for laser pickup, it was never rebalanced. You'd have to stand and keep your ass of the seat and hold onto the bars with only two finger while you gridded for your race because anything in contact with the bike would go numb. Once rolling you would rev it untill it vibrated so bad it felt like the piston was going to shoot through the tank then count to 3, then shift
that bike was one of the most insane machines I've ever ridden, I only wish it didn't put my whole body to sleep from vibrating so damn much. I've never heard anything can anywhere near the speed that bike would rev in neutral.