How to limit speed of gy6 cart

[J2theV]

Hi I have a twister kart that's goes faster than i'd like. Is there a way to limit the speed of the kart so it's safer for my 10 year old? Right now it goes 35-40 mph. I'd like to make the top speed 20-25 mph but still have power to climb hills.
Thanks

[SYCARMS]

If it has the old AC CDI then no, if you have the later DC volt CDI I'll have to check but I should be able to get a restricted CDI that will limit it to 25mph max.