Q. Why won't my scooter start?
Begin by going through the troubleshooting steps in the link below. If you still cannot get your scooter to start, create a thread in an appropriate section of the forum and provide as much detail as possible related to the issue.
No-Start Troubleshooting
There are three things that you will almost always be asked to verify when you ask about a non-starting scooter that will turn over (the engine rotates via the kick starter or electric starter) on the forums. This is because these three things are essential for reliable combustion and common causes of no-start conditions. There is more detail about each in the No-Start Troubleshooting thread, but they are :
- Does it have spark? Checking for spark is quick and easy so it's one of the things that you may want to check for first. Remove the spark plug from the engine. Attach the boot/cap to the plug. Hold the metal portion of the plug against a good ground, such as a metal part of the engine or frame. Be sure to hold an insulated part to avoid being shocked. Kick or crank the engine over and you should see multiple sparks. Hopefully the sparks will be white/blue/purple and consistent. Inconsistent sparks or orange sparks may be a problem. Here's a VIDEO showing the easiest method.
- Does it have compression and/or how much compression? Using a compression tester so you can see how much compression the engine has is by far the best way to troubleshoot. You want to see at least 90-100psi if you expect the engine to start, although even those numbers are low for the typical healthy engine and may indicate a problem. Most strong running engines will show around 150psi or higher. Always make sure the throttle is held wide open and that you are cranking the engine over quickly enough. I often use the electric starter at first, then switch to the kick starter to be sure I've reached the max pressure reading.
In a pinch you can remove the spark plug and put your thumb over the spark plug hole. Obviously don't try to put any digits into the plug hole, only do this with a cool engine, and make sure nothing has broken inside of the cylinder (valve, chunks of metal) that could be pushed out into your thumb. When the engine is kicked or cranked over the force of compression should try to push your thumb off of the cylinder.
You can also try to rotate the engine over by hand while the spark plug is still installed. You should feel a strong resistance when the engine approaches TDC (Top Dead Center) and then it will get easier as you turn past TDC and repeat this process if you continue to rotate the engine. - Does it have fuel? The easiest way for a quick check is to look at the spark plug when you remove it to check for spark or compression. If the engine has been cranking over, you should see some trace of fuel on the plug or it may even be saturated with fuel. This tells you there is indeed fuel getting to the cylinder. It could even be an indicator of a flooded engine (too much fuel), in which case you may try leaving the plug out for a bit so it can clear out and/or cranking the engine over a few times while the plug is out. If the engine is flooded, it may start if the throttle is held all the way open. If the plug is totally dry when you check it after attempting to start the engine, fuel is probably not making it to the cylinder and the carburetor and fuel system should be checked over.
You should also think about how old the fuel is. If your scooter has sat for an extended period of time with fuel in the tank or the gas you've used it old (usually more than 2 months), the fuel may not be suitable for use. Sometimes you can clearly smell that the fuel has gone bad as it may get a varnish smell. Sometimes fuel gets water in it, you can even get watery gasoline from the pump. Draining a bit of gas into a clear fuel-safe container (a glass jar should work) and letting it sit for a while will show you if there's water in the fuel. Water is heavier than gasoline so it should settle to the bottom and you should be able to see the separation.
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