Four-stroke dirt bike won't start after a tip-over: clear the flood

Applies to: Yamaha YZ250F/FX, KTM SX-F and other four-stroke dirt bikes

Symptoms

  • Won't restart after a crash or tip-over
  • Strong fuel smell, wet plug
  • Fires once and dies

Why it happens

When the bike lies down or stalls hot, extra fuel runs into the engine and wets the plug. More cranking with the throttle shut just adds fuel.

How to fix it

  1. Pick the bike up and let it sit a moment.
  2. Hold the throttle wide open (or use the hot-start) and crank or kick to clear the cylinder.
  3. If it still won't fire, pull and dry the plug, or fit a new one.
  4. Check the air filter didn't get soaked or dirty in the crash.

Tools and parts

  • Plug wrench
  • Spare spark plug

What the factory service manual covers

Starting procedures, spark plug spec, fuel system. The full procedure, specs and wiring diagrams are in the factory service manual for your machine.

Get the factory service manual

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