The top three reasons why your moped isn't running are A.) a dirty carburetor B.) a faulty spark plug, or C.) worn or mis-adjusted ignition points. The most common reason is a dirty carb. If your moped isn't even running, the first thing you should check is to see if the spark plug is working. First, pull out the old spark plug and put a brand new one in the cap. Hold the metal part of the plug firmly against the cylinder head while you pedal rapidly with the key and switch on. If you see a blue spark on the spark plug, then that is good. If you don't see a spark, then clean the ignition points.

To clean the ignition points, use sandpaper, a piece of clean paper, a pair of scissors, some aerosol brake or carb cleaner, and some compressed air. Take off the ignition cover and look for the points in one of the holes in the flywheel. When you find them, lay the bike on its side and sit on something to get situated. Next, pry the points open with a small screwdriver and stick the small pieces of sandpaper (about 1/4" wide, 3" long) in between the points and let them close. Now pull out the sandpaper. Do this a few times to each side until they're smomoth. Then, pry the points open and blow them with compressed air and spray them with cleaner. Now, pull a piece of regular paper through the points to see if they come out clean and smoothly. Blow the points off again with some air and they should be good to go.

If there IS a spark, but the moped still doesn't run, squirt a spoonful of gas into the spark plug hole and try starting it. If it starts and runs for five seconds and then dies, check for fuel flow to the carb. To do this, take out the fuel line going into the carb and turn the gas on. If it doesn't flow freely out of the gas line, then you may have a vacuum operated petcock (if you do there will be another rubber line going from the engine to the petcock). Take this second line off the engine or carb and suck on it. Check for fuel flow out of the other line. If there still is none, then take off the petcock and clean it.

Dirty carburetors are the number one reason for poor moped performance. The small holes in the carb (where the air and fuel pass through) are what is dirty. You need to use compressed air to blow the dirt out. Remove the float bowl from the bottom of the carb, then try to blow air through it. If you look through and it's not clean and clear, push a piece of thin wire through. Then, use aerosol carb cleaner and compressed air to clean out all passages in the carb. Squirt the cleaner in all the small passages, then blast some air in. Do this in each direction several times, then reassemble the carb. If you can soak the entire carb in a can of cleaner overnight (remove rubber and plastic parts), even better. Then blow it out the next day.

Good luck in your quest to get your moped up and running. If all else fails, take it to a mechanic, who can do a thorough inspection to see if something major is wrong with the bike.