This is a little trick we came up with When our first son
got his first dirt bike, a 1998 KTM pro junior. When he first
rode the bike it was immediately obvious that the bike had
way too much power for a 6 year old on his first bike. It
scared him and we wanted to save any damage we could
on the bike, the rider, or any object of value that might be
in his way.
The trick we came up with was a throttle stop in the form
of a piece of pvc pipe in between the throttle valve and the
cap to limit the throttle valve from opening any more than
we wanted it too. We played with allot of different ideas
before we came up with this, but this was the only solution
that allowed us a positive control that could be tuned. We
ended up with 2 different sizes. One to start with that would
barely allow him to open the throttle and one just a bit more
aggressive. It was amazing how quick we were able to
remove the stop after he learned to ride and control the
bike. Our second son just turned 6, and the KTM was
passed down to him, so we just need to find the spacers
and start over again with him. It's an easy, out of the way,
solution that worked every time and that can be tuned to
each bike. I am fairly sure that it will work on any bike with
a round throttle tube, you'll just have to experiment to get the right length of pvc.