My son (6) has a Yamaha TTR50cc dirt bike. Gears are three up, no clutch. The other day he was trying to get it into gear and was having trouble. I grabbed the left grip and told him to hop off for a second. He dismounted off to the right, his boot got stuck under the gear shift and sure enough it went into gear while he was dismounting. The popping caused him to panic and hit the throttle. He's running with the bike now. I'm shouting let it go. It's heading towards Mama's Volvo. Everything turned out OK, just a divet in the yard. But, it did get his attention. "Dad, I think I forgot to hold the brake while I was gettin' off". I explained to him everything that happened, was thankful that he was not injured, and reminded him to remember so that we could avoid the same situation in the future.
I mount/dismount from the left due to hot pipes on the right.