KTM 85 SX

The 85 SX is the junior race bike that wins. It makes more power than the Japanese 85s, it has a hydraulic clutch and better brakes, and it has had the most development of any bike in the class. The big wheel version with 19 and 16 inch wheels suits taller kids. It got a new generation in 2018 and updates since, and it is the same bike as the Husqvarna TC 85 and GasGas MC 85.

It suits a junior who is racing seriously and needs the fastest bike. It is snappier and more demanding than a YZ85, so a first time 85 rider or a smaller kid may be better on the Yamaha. The trade off is price: it costs more new and holds its value used.

Premix at 40:1 to 60:1 with a good full synthetic (KTM says 60:1, most racers run a little richer), gearbox oil every 5 to 10 hours (about 500 ml), air filter every ride. A racing 85 wants rings every 10 to 15 hours and a piston every 20 to 30. Clean the power valve at every top end.

The hydraulic clutch uses mineral oil on most years; check the reservoir cap. Check the air fork pressure before every ride on the bikes that have one, and keep the spokes tight.

Buy a bike that a family raced and serviced, with receipts for the last top end. A compression test tells you most of what you need to know. Check the frame around the footpeg mounts, the subframe and the radiators for crash damage. Make sure the clutch lever is firm and the air fork holds pressure. Racing 85s get crashed; the question is whether anything is bent.

Recent sold prices are on the Marketplace page linked below.