i have a 10 year old that races nitro with me all the time. He starts them up himself and all now, tuning can be an issue but i am there when its run time. He also has 3 bikes, 2 dirt bikes and one cafe racer, all 50cc. Nitro will give him longer run times. there is not after market stuff but redcat makes plenty of hop ups like aluminum for it.

http://redcatracing.com/parts_search...&partscat=6000