This item originally appeared on the Myron's Mopeds webpage.

Moped Repair Tutorial

(Note: I am not the author of this tutorial. It was originally written by someone calling themselves the 'Moped Guru'. I've place this local copy on my site because I found it very helpful in working on mopeds, but I cannot guarantee its accuracy. -JCN)


This guide is for mopeds only and will solve about 90% of the problems people encounter when trying to fix their mopeds. If you own a scooter that doesn't have pedals such as a honda express or vespa the following manual doesn't apply, only motorized bicycles are covered here.

Before you begin:

All mopeds are metric, you will therefore need some basic metric tools. This list describes some of the tools you may need:

Start Trouble Shooting Here.

All moped repairs begin with trouble shooting. The following outline describes the most common symptoms.
If your moped falls into any of the above catagories, this manual will help you get you 'ped up and running.

Step 1 Testing for spark and fuel flow.

Follow these instructions even if you think there is no spark !!!!!!
Note: I have repaired a hundered or more mopeds using this guide line.
At this point one of two things will happen:

Step 2 Checking for fuel flow. The most common problem!

The most common problem with mopeds is thay have been stored for a long period of time with fuel inside. The fuel turns bad and clogs the bikes natural fuel flow. In most cases the carburetor will need to be rebuilt (or I should say cleaned) and the bad fuel drained, in some cases the fuel turns into a varnish in which case you will need to flush out the fuel tank and clean or replace the fuel valve as well.

Fuel flow in a basic moped is very simple. Fuel travels from the gas tank through a fuel valve and fuel line to the carburetor where it enters a float bowl. From there the fuel is sucked through a fuel jet by the venturi effect and mixed with air and injected into the crank case (not the combustion chamber but just behind the piston. This is how all 2-stroke mopeds lubricate the bottom end). From the crank case the air/fuel mixture enters the cylinder head through a port that travels up the inside of the head and is burnt, then exits through the exhaust port. Back to Step 1.

Step 3 Checking for spark.

There are about seven electrical components on the average moped ignition system. they are:
Now you may be wondering why I put tail lights on this list. Most people wouldn't think that the tail lights would be on the ignition system but they are. Much like on a car where the horn is on the brake light system so you can test your horn to see if the fuse to the brake lights is working, some moped engines won't run unless the tail light is working properly.

Step 4 Tail lights.

To test to see if the tail light maybe the problem.
Now go back to step 1 to see if this did the trick.

Step 5 Kill/Run Switch.

Mopeds don't have keys, they have kill switches. All the kill switch does is ground the ignition system. Sometimes the wire or the switch itself will become grounded. The test to see if the switch is the problem is to simply disconect the switch from the system. It's best to disconect it as close to the engine as possable. Follow the wire from the switch down the frame to the engine and disconnect it.

Back to step 1

Step 6 Contact breaker points.

Up to this point I have presented you with the most common problems and their solutions so if you have gone through the first five steps and your moped still doesn't run then it's time to test the points to see if thay are opening. There are two ways to do this.
Back to step 1
Step 7 Spark plug cap and wire

If you have come this far and your moped still isn't running then it's time to replace the spark plug cap and wire. The spark plug cap and wire only cost a few bucks to replace and there's really no easy way to test them unless you have a cap and wire that you know are good.

Back to step 1

                                       Myron's Mopeds
                               1879 W Commonwealth Ave. Unit L
                                   Fullerton, California 92833