A Yamaha XSR155 that will not start is usually held back by a switch, a flat battery or a fuel fault. The six-speed manual transmission adds a clutch switch and a neutral circuit to the usual checks, and both are easy to test.
Before you start
Petrol, battery acid and a hot exhaust are all present. Do not check for spark with a bare hand or near the tank, and do not bump-start on a slope with traffic behind you. Wear gloves when handling a hot plug.
Machine file Yamaha XSR155
- Engine
- Liquid-cooled four-valve SOHC single with VVA
- Cooling
- Liquid
- Fuel
- Fuel injection
- Transmission
- Six-speed manual
- Final drive
- Chain
Manual bikes fail differently
A scooter starts in any gear as long as a brake is held. A motorcycle with a manual gearbox needs the transmission in neutral, or the clutch pulled in, before the starter is allowed to work. That logic is the first thing to confirm.
If the neutral light is out and the clutch switch is faulty, the starter will not run even though the battery is perfect. Test both before removing a panel.
XSR155 start checks in order
| Check | Normal | If not normal |
|---|---|---|
| Neutral light | Lit in neutral | Shift to neutral, check sensor |
| Clutch switch | Starter works in gear | Inspect lever connector |
| Side stand | Up and switch closed | Check spring and plunger |
| Kill switch | Run position | Switch to run |
| Battery | Fast, even crank | Charge, test, clean terminals |
| Fuel pump | Whine at key-on | Check fuse and connector |
Clutch switch and neutral light
Sit on the bike, turn the key and watch the neutral indicator. If it lights, the gearbox is in neutral and the starter should be permitted. If it does not, shift down through the gears until it does.
Then pull the clutch and try again. A clutch switch that has failed will block the start with the bike in gear. Check the small connector at the lever perch for corrosion or a loose fit.
Side stand and kill switch
The side-stand switch cuts the engine if the stand is down and a gear is engaged. A sticky plunger or a stretched spring can leave the circuit open, which prevents the start or kills the engine as soon as you select first.
Check the engine stop switch on the right bar as well. It is the most common cause of a silent start after a service or a wash, and it is the easiest thing to overlook.
Battery and cranking speed
A fuel-injected single needs a fast, consistent crank for the ECU to synchronise and fire. A battery that turns the engine slowly may be past the point where it can start the bike, even if the dash looks normal.
Measure the voltage at rest and while cranking. Clean the terminals and the earth strap, and check the main fuse. A jump from a 12-volt donor is acceptable with the correct polarity.
Fuel, spark and compression
If the engine cranks strongly and does not fire, check the fuel level and listen for the pump at key-on. A bike stored for months may have stale fuel and a varnished injector.
Remove the plug and read its colour. Wet and smelling of fuel points to an ignition fault; dry points to fuel delivery. A compression test is the next step if both are present and the engine still will not catch.
What a bump start proves
A bump start can help a manual bike with a flat battery, but only if the battery can still run the pump and the electronics. If the dash dies when you turn the key, pushing the bike will not help.
Bumping a fuel-injected bike with a dead battery can also flood the engine and damage the catalytic converter. Charge or jump the battery instead, and treat a bump start as an emergency measure on a firm, quiet surface.
Keeping it from coming back
The XSR155 is a manual bike, so the clutch switch, neutral sensor and side-stand switch are part of the start circuit. Keep the battery charged, use fresh fuel, and check those switches before cranking. A bike that stands for weeks is better charged than idled, and the battery is small enough that a marginal one shows up as a slow crank.
A short checklist
- Confirm the neutral light and try the clutch switch.
- Check the side-stand switch and the kill switch.
- Measure the battery at rest and while cranking.
- Clean the terminals and check the main fuse.
- Listen for the fuel pump at key-on.
- Read the spark plug before ordering ignition parts.
Questions owners ask
Why does my XSR155 not start in gear with the clutch pulled?
The clutch switch is not telling the ECU that the lever is pulled. Check the connector at the lever perch and the switch plunger. Until it is fixed, start in neutral.
Can I bump-start a fuel-injected XSR155?
Only if the battery can still power the pump and the ECU. With a fully flat battery the injection will not run, and pushing the bike may flood the engine. Charge or jump it instead.
The engine cranks but will not fire. What is the first check?
The spark plug. Its colour tells you whether fuel is arriving. Wet and smelling of petrol points to ignition, dry points to the injector or pump.
