Dirt bike maintenance schedule: what to check and when

A motocross bike is serviced by engine hours, not by kilometres or miles. A full-size race bike works hard every minute it runs, so parts wear on a schedule you can predict if you know how many hours are on the engine. Missing an oil change or a dirty air filter is how a cheap service turns into an expensive rebuild.

The intervals below are typical ranges for modern 250 and 450 motocross bikes. Your owner's manual always wins. It lists the exact intervals for your model, and many manuals give shorter "racing" intervals. If you race, ride in deep sand, or the bike is ridden hard by a fast rider, use the short end of every range.

After every ride

These take 20–30 minutes and catch most problems before they become failures:

• Air filter: inspect it. In dusty conditions clean and re-oil it after every ride. Always keep a clean, oiled spare ready.
• Wash the bike, but avoid pointing a pressure washer at bearings, seals, the airbox and electrical connectors.
• Chain: clean, lube and check the slack. Check the sprockets for hooked teeth.
• Spokes and wheels: check spoke tension, especially on a new bike or after a new tyre.
• Bolts: check the important ones: axles, pinch bolts, triple clamps, engine mounts, sub-frame, footpegs and handlebar clamps.
• Fork seals: wipe the dirt off the seals and check for oil on the tubes.
• Coolant, brakes and cables: check coolant level, brake pads and fluid level, and the clutch and throttle cables for free play.
• Tyres: check pressure and look for cuts and missing knobs.

Engine oil

• 4-stroke: engine oil roughly every 5–10 hours. Replace or clean the oil filter at least every second change; many riders do it every time.
• 2-stroke: gearbox oil roughly every 10–20 hours.

Fresh oil is the cheapest insurance you can buy. If the oil comes out very dark, metallic or milky, find out why before you ride again.

Air filter

Treat this as the most important item on the list. One ride with a torn or badly seated filter can let in enough dust to wear the piston and rings. Check that the filter seals evenly against the airbox every time you refit it, and grease the rim if your manual says to.

Top end and valves

• 2-stroke top end (piston, rings, small-end bearing): often every 30–60 hours, depending on the bike and how hard it is ridden. A drop in power or harder starting is a sign it is due.
• 4-stroke valve clearance: check roughly every 15–30 hours. Tightening clearances on the intake side are a warning that the valves are wearing.
• 4-stroke piston: usually far longer than a 2-stroke, but at the interval in your manual. Racing manuals often specify much shorter intervals than trail use.

Suspension service

• Fork oil and seals: a fork service roughly every 20–40 hours. Damping fades long before the oil looks bad.
• Shock service: roughly every 30–50 hours.
• Linkage, swingarm and steering head bearings: clean and re-grease roughly every 20–40 hours, and sooner if you ride in mud or wash with a pressure washer.

If the bike starts to feel harsh or vague and your clicker settings have not changed, the suspension is probably due for a service.

Chain and sprockets

A chain kept clean, lubed and correctly adjusted lasts much longer. Replace the chain and both sprockets together; a new chain on worn sprockets wears out quickly.

Once a year (or every season)

• Coolant change
• Brake fluid change, front and rear
• Clutch and brake lines checked for wear
• Spark plug (or at the interval in your manual)
• Wheel bearings and seals

Keep track of the hours

All of this depends on knowing the engine hours, and most motocross bikes either have no hour meter or one that nobody remembers to write down. MX Rider Pro adds the time of every recorded ride to the bike's engine hours, keeps a log of what was serviced and when, and can remind you when the air filter, oil or another service item is due, so you change the oil because it is due and not because you suddenly remembered.