Gas Dirt Bikes & Pit Bikes

The FX125 tops out around 56 mph and the FX140 hits about 65 mph — real speed depends on rider weight, gearing and terrain. More on how cc translates to top speed.

Around 12, most riders fit the FX125 in the smaller 14"/12" size (28.1" seat). Match height and inseam with our dirt bike size chart by age, or see the best dirt bikes for 12-year-olds.

The FX125 and FX140 both hold up to 265 lb, so they carry teens through adults; the FX40 is rated to 132 lb. Full breakdown of dirt bike weight limits.

In the 17/14 build they share a chassis — same 33.9" seat, same 49.2" wheelbase, same 265 lb load. The difference is the engine: the FX125 is air-cooled, 8.7 hp / 8.8 N·m, rated to climb 28°; the FX140 is oil-cooled, 11.0 hp / 10.2 N·m, rated to 30°. Oil cooling holds that power up on long climbs, hot days, and hour-long sessions, where an air-cooled engine starts to fade. For short sessions in the yard, cooler weather, or a lighter rider, the FX125 is enough. We break it down in the 125cc vs 140cc dirt bike guide.

A taller teen fits the FX125 in the 17"/14" build (33.9" seat) or steps up to the FX140. See what size dirt bike for a teenager.

No — FRP dirt bikes are EPA off-road models, not registered for public roads. Ride them on private property, trails and off-road areas (the FX40 and FX140 are not sold in California). More on whether a dirt bike is street legal.

Regular unleaded pump gasoline — every FRP FX is a four-stroke, so you fill the tank with gas only and add no oil to it. Follow the octane and ethanol limits in your owner’s manual, and don’t leave old fuel sitting in the tank for weeks. More in what type of gas a dirt bike needs.

The FX40 is the smaller, automatic 40cc option, rated to 132 lb and about 20 mph, so a new rider can focus on throttle, braking and balance. See gas dirt bikes for 7, 8, 9 and 10 year olds and what size dirt bike for an 8 year old.

No — every FRP FX is a four-stroke, so there is no fuel-and-oil premixing. See how to choose the right engine oil.