How do I Troubleshoot a 50cc Scooter?

Written by tom lutzenberger
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Scooters require fuel, air, compression and spark. Without these factors being in place, the scooter engine won't run properly. Troubleshooting a 50cc scooter typically focuses on the areas that affect either combustion or the fuel-to-air ratio. Electrical systems can be a source of problems, but the engine tends to be the primary focus of repair.

Skill level:
Moderately Easy

Things you need

  • Socket wrench and sockets
  • Shop towel
  • New spark plugs
  • Spark-plug tester tool

Show MoreHide


    Eliminating Human Error

  1. 1

    Turn the ignition key to the "on" position. Check that the kill switch is also in the "on" position, and not cutting off the circuit. Press down on the rear brake-lever with your foot; this is a safety feature that must be in place to start modern scooters. Press the ignition button to see if the engine will start.

  2. 2

    Squeeze your front brake -- or reposition the scooter's stand -- if your scooter requires these features to be engaged to start.

  3. 3

    Turn the ignition to the "off" position. Manually remove the sidepanel that covers the battery. Turn the ignition to the "on" position, but do not start the scooter. Check your indicators on to see if they work. Do the same for the rear brake. Replace the battery or recharge it if the lights don't work. Make certain the fuse for the system is still intact and not burnt out.

    Checking the Combustion Process

  1. 1

    Put the scooter in the "on" position. Turn the fuel flow on. Use your foot to kickstart the engine; give the scooter about two to five good kicks. Pull the throttle to allow more gas if the engine starts to turn over.

  2. 2

    Take the scooter off the kickstand so that it can roll. Shift the scooter into neutral. Push the scooter down the street so it has some momentum. Quickly jump on and shift into first gear while pulling the throttle. This will bump-start a manual-shift scooter if it is flooded.

  3. 3

    Pull the sparkplug cap off the spark plug. Use a socket wrench to remove the spark plug. Insert a spark-tester tool into the plug socket in the cylinder. Kick the scooter over with the kickstart pedal to see if the tool lights up. If so, the ignition coil is bad and needs to be replaced.

  4. 4

    Use a screwdriver to disconnect the fuel line from the carburettor. Hold the fuel line end in your hand with a shop towel. Turn on the fuel flow. Watch the end to make sure the fuel is flowing correctly. Turn it off and reconnect if there is fuel flow.

Tips and warnings

  • Replace your spark plug regularly even if you don't think it needs it. Plugs are cheap and tend to be major cause of ignition problems .

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