A bike that ran well before it was parked now will not start. Several things go wrong while a bike stands: the battery goes flat, fuel goes stale and leaves sticky deposits in small carburettor jets and filters, water collects in the tank, and animals chew wires or nest in the air box or exhaust. Work through them in order before cranking for a long time.
Is it safe to ride?
Not until you have done the checks in Bring a bike back into use after storage. Brakes, tyres and chain also suffer from standing.
Quick checks first
- Look in the air box and exhaust outlet for nests, rags or insects.
- Look for chewed wires under the seat and around the battery.
- Smell the fuel: sour or varnish smell means stale.
- Do the dashboard lights come on with the key ON?
- Check tyre pressures before moving the bike far.
Diagnose it step by step
1Does the engine crank at normal speed?
- No: the battery is flat or worn. Test and charge a 12 V battery. The K-Light 125 manual says to charge a stored battery about every 3 months; a battery left flat for months may not recover.
- Yes: go to step 2.
2Are there chewed wires, or is something blocking the air box or exhaust?
- Yes: clear the blockage and repair wiring. Find a wiring fault.
- No: go to step 3.
3Is the fuel fresh, without water or dirt?
- No: drain it and refill. Drain old or contaminated fuel. See Old or stale fuel in the tank and Water or dirt in the fuel.
- Yes: go to step 4.
4Is there a strong spark and a clean plug?
- No: Remove, check, gap and fit a spark plug, then No spark at the spark plug.
- Yes: go to step 5.
5Carburettor: does fresh fuel come out of the float bowl drain screw?
- No: the tap or filter is blocked: Check the fuel tap, lines and flow. Rust flakes: Rust or flakes inside the fuel tank.
- Yes, but it still will not start, or starts only on choke: the jets are gummed up. Clean the carburettor.
6Fuel-injected: does the pump run at key ON?
- No: Check the fuel pump (fuel injection). K-Light 125: the pump runs about 3 s at key ON.
- Yes, but no start: the filter or injector may be blocked by old fuel. Replace the fuel filter, then have the injector checked.
Electric motorcycles: see Small 12 V battery is flat instead.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Flat or ruined battery | Slow or no cranking; low voltage | Test and charge a 12 V battery |
| Stale fuel | Sour smell, dark colour | Drain old or contaminated fuel |
| Gummed carburettor jets | Fuel at drain but no start or choke only | Clean the carburettor |
| Blocked tap, filter or rusty tank | Weak flow; flakes in filter | Replace the fuel filter |
| Fouled plug | Plug black or rusty | Remove, check, gap and fit a spark plug |
| Chewed wires or nests | Visible damage | Find a wiring fault |