Hi 

looking for some advice please, I’ve got my girlfriend a gas gas jtr 125 and was wondering if there is any way to restrict it while she learns? 
 

thanks 

Slow action throttle probably the easiest and cheapest. Check what's on it now, white throttle tube is fast, black is slow.

 Make a stop inside the slide. Let it only go half throttle.

Domino make a throttle body with a variable opening using a screw to restrict full throttle. Splatshop have a picture of one. I have one for use when starting a new or tentative rider. Also here is a blog of a DIY modification https://thehellteam.blog/2018/10/30/making-a-restriction-for-the-domino-throttle/

The easiest and cheapest way is to put a pit of fuel pipe over the throttle cable on the carb end