The bike started fine when dry, but after heavy rain or a wash it cranks without firing, or the starter does nothing. Water lets the high voltage leak away before it reaches the plug, shorts switches and connectors, or gets into the air box or fuel. Pressure washers push water into places rain never reaches. The K-Light 125 manual notes that most ignition faults are poor connectors (PDF page 85).
Is it safe to ride?
With care once it runs. If it misfires or cuts out after it starts, wait until it is properly dry: an engine that stops in wet traffic is dangerous.
Quick checks first
- Pull off the plug cap: is there water in the cap or in the plug well around the plug?
- Flick the engine stop switch and the key a few times.
- Look in the air box: is the filter wet?
- Has the bike been washed with a pressure washer near the headlight, switches or under the seat?
- Is the fuel cap seal good? Could water have entered the tank?
Diagnose it step by step
1Is there water in the plug cap or around the plug?
- Yes: dry the cap and the plug well with a cloth or compressed air before removing the plug (so water does not fall into the cylinder). Check the cap for cracks. Test the ignition coil and plug cap.
- No: go to step 2.
2Does the starter work and the dashboard light up normally?
- No: water may be in the handlebar switches or the key switch. Test the engine stop switch, Clean a handlebar switch.
- Yes: go to step 3.
3Is there a strong spark on a spark tester?
- No or weak: dry and clean the coil, cap and connectors, especially the ones under the seat and in the headlight shell. Clean and seal electrical connectors. Then test again: Check for a spark safely.
- Yes: go to step 4.
4Is the air filter or air box wet?
- Yes: drain the air box, dry or replace the filter: Clean or replace the air filter. If water may have been sucked into the engine, do not keep cranking; ask a workshop.
- No: go to step 5.
5Carburettor: is there water in the float bowl (drain a little into a clear jar and look for drops that sink)?
- Yes: water got in the fuel. Water or dirt in the fuel and Drain old or contaminated fuel.
- No: let the bike dry in the sun or a warm place and try again. If it never starts when dry either, go to Engine turns over but will not start.
To prevent it: wash by hand or with a low-pressure hose, keep water away from switches, cap and air intake, and put a little dielectric grease on connectors.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Water in plug cap or plug well | Wet cap; weak or no spark | Dry it; Test the ignition coil and plug cap |
| Cracked plug cap or lead | Tracking marks; sparks on wet cap | Replace cap or coil |
| Wet handlebar switch or key switch | Starter or dash dead when wet | Clean a handlebar switch |
| Wet connectors | Green corrosion; works when dry | Clean and seal electrical connectors |
| Wet air filter | Water in air box | Clean or replace the air filter |
| Water in fuel | Droplets in float bowl sample | Drain old or contaminated fuel |