The TTR50E that I have has a kill switch with remote trigger. It was installed by the previous owner. I theory, if your kid goes WFO and loses control, you push the button and it kills the engine. I never needed it for my son, even though he liked to go FAST. Somehow, he always managed to keep it reasonably under control. I could have used it for my oldest daughter, but she was on a runaway XR80R that did not have the switch. Also, the throttles on a lot of the little bikes have a screw/bolt you can turn to act as a throttle stop, setting the max throttle you can do. I never used that either just because the bolt was missing on mine and I never got around to using it. The girls pretty much never went wide open and my son would have figured out how to remove it... We sometimes had to look away when he was riding [emoji38]2:
These are at my folks place. They have more room to ride that my place. He figured out the driveway could work as a flat top jump when I wasn't looking. Then he had to show off once I realized what he was doing.
He was so pumped from riding when we got home, he wanted to ride Sarah's CRF 110.
By the way, that jacket he is wearing has been great. I think it was around $100, but it has help up really well. He was 7 when I shot these pics. He has only recently outgrown it. He used it on the street as well, riding on the back of my 1200 GS, but usually with some kind of wind breaker over it when it got cooler. He's finally big enough for a small street based textile jacket to fit. He's got knee pads on under the pants. If you can't find decent pants protection for your son, go to Academy and look at the football pants. They have knee, hip, thigh, and tail bone padding. My kids wear those under the dirt pants for dirt riding and street.