When diagnosing a no-start condition on a scooter, there are several steps you can take to identify the problem. Here's a general diagnostic procedure you can follow:
Check the basics:
- Ensure that the scooter has fuel in the tank.
 - Verify that the kill switch is in the "on" position.
 - Check the sidestand or center stand switch, as some scooters won't start if the stand is down.
 - Confirm that the scooter is in neutral (if applicable) or that the clutch lever is pulled in.
 
Inspect the battery:
- Check the battery connections for corrosion, looseness, or damage. Clean and tighten them if necessary.
 - Measure the battery voltage using a multimeter. It should ideally be around 12.6 volts or higher for a fully charged battery. If it's low, charge the battery and retest. If it doesn't hold a charge, the battery may need to be replaced.
 
Check the spark plug:
- Remove the spark plug and inspect it for fouling, damage, or excessive wear.
 - Check the spark plug gap using a spark plug gap tool. Adjust it if necessary.
 - If the spark plug is fouled or worn out, replace it with a new one.
 
Verify the ignition system:
- Check if there is a spark when the engine is cranked. You can do this by grounding the spark plug against the engine while it's still connected to the spark plug wire and observing for a spark during cranking. If there's no spark, the ignition coil, spark plug wire, or CDI unit may be faulty and require inspection or replacement.
 
Assess the fuel system:
- Ensure that fuel flows freely from the tank to the carburetor or fuel injector.
 - If the scooter has been sitting for a while, the carburetor or fuel injector may be clogged. Clean or unclog them as needed.
 - If the scooter has a fuel pump, check its operation.
 - If you suspect a fuel-related issue, you can also try spraying a small amount of starting fluid into the air intake to see if the engine starts momentarily. If it does, it indicates a fuel delivery problem.
 
Check the air intake and filter:
- Inspect the air filter for dirt, clogging, or damage. Clean or replace it if necessary.
 - Make sure the air intake is clear of obstructions and debris.
 
If you've gone through these steps and still haven't identified the problem, it may be necessary to consult a professional mechanic or refer to the specific troubleshooting procedures outlined in your scooter's service manual.