Had a near miss at the weekend with my 4 year old on his 12.5. He was riding down a short steep hill when the throttle has gone forward past the off stop position. The throttle then operated as full throttle and the bike took off crashing with him into a wall. Thankfully my son was fine. The oset has twisted bent forks and buckled wheel. I emailed oset uk with the details however to date no response. I would expect the default position with any failure should be to zero rather than maximum. At least with a petrol bike you have a kill switch.

on the the oset they have a key? cant you just have something like string on your sons wrist and on the key so if he do's fall of it put the key out and turns off the bike?

(know nothing about osets, just thinking of what ive seen)

It is possible to run a normally closed circuit lanyard so when your child falls off the bike stops:

http://www.splatshop.co.uk/lanyard-kill-switch-non-magnetic.html

Or you can use an On/Off switch as a stop button:

http://www.splatshop.co.uk/kill-light-switch-on-off-toggle-switch.html

This is a good topic. These days I let no new riders (including neighbor kids, etc), touch an OSET unless they have done a series of tests first. I guess I have learned the hard way.

Things I do before lending the bike to a new rider:

1) The first of these tests is to check for the new rider's ability to give it full throttle and hold the rear brake tight enough so that the bike will not go anywhere.

2) With the kickstand, I lean the bike over so that the rear tire is in the air, and have the new rider show me throttle control: very slowly increasing and backing off the throttle, as well as the ability to "whack" it to full throttle and immediately back off.

3) Show an ability to find the rear brake quickly after my prompting a few times.

4) Be able to ride a short distance and then slam on the rear brake hard.

Yet, once, I turned my back on my son as I spoke with a neighbor for a second, and before I knew it, his son rode past us and slammed into a parked car. How did this happen? My son had let him get on the bike for a moment and then the magic of "whiskey throttle" whisked the unwitting boy away. Glad he did not get seriously hurt. My kids now know to not let other kids get on or even touch the bike with the ignition on.

I considered a radio controlled kill switch mod but I think the range was only about 200ft.

Big thanks to Ian at Oset UK bike now sorted. All parts replaced FOC as goodwill gesture. Old throttle returned for them to check problem.