i never used to get tired on scooters but now after like 30 mins of riding my forearms get tired and fell sore i just learned bars and bar-twists flat could that be a problem, also is there a way to stop bruising your hand when you bar-twist
You're hands are probably just not use to the impact from catching a barspin yet. When I first learned barspins on bars that weren't stock, they use to hurt my hands when I caught them. Your body should adjust.
The impact of bars on your hands can be counter acted by catching the bars early and bringing them round. Its harder to do for spin barspins though (ie trucks)