hmm 5? Id say a 90. 2 strokes are faster, but require more mintenance.. just a personal preferance. Dont bother looking at the manufactuers suggested age limit... Im technically not supposed to ride my 250 yet and Im already lookin for a 450. go figure

 

No every 5yr old is the same size nor is every 80cc or 90cc kids quad. Put the kid on a few different models and see how they fit. Can they reach the floorboard and be able to lift their butt of the seat? Can they squeeze the brake levers (most important)? Can they turn the handlebars from side to side without struggling?