Testing the Fuel Enricher on a Chinese 4 Stroke Scooter QMB139

On the QMB139 type engines, the carburettor is on top of the engine under the seat. The fuel enricher is heated by electricity (12v) supplied by the 4 stroke scooters magneto/battery. The electricty warms the enricher expanding the wax inside. This expansion pushes a plunger which blocks the extra supply of fuel.

1. Expose the fuel enricher by removing the under seat panel.
2. Undo the cross head screw that secures the enricher to your 50cc 4 stroke scooters carburettor. Access is limited so in the picture we are using a ratchet wrench fitted with a cross head attachment.
   
   
3. Once the retaining screw has been removed you can remove the fuel enricher from the carburettor. Take care not to damage the rubber seal or to let dirt into the opening on the carburettor.
4. Undo the electrical connector that connects your imported scooters fuel enricher to the wiring loom.
5. Next, you will need to apply 12v to the scooters fuel enricher and measure the effect on the plunger over time. To do this, carefully remove the pins from the fuel enrichers connecter using a long thin screwdriver to release the tabs. NOTE: this is not strictly necessary but it makes it easier to apply 12v to the enricher.
   
   
6. Now measure the length of the fuel enricher when cold. In this example we have attached the enricher to a metal rule so we can clearly see the expansion take place. Our enricher was 58mm cold (NOTE: yours may be different. The important thing is that it expands enough to close the flow of extra fuel once warm!)
   
   
7. Leave the 12v supply attached to your QMB139 Chinese 4 Stroke scooters fuel enricher for at least 5 minutes. You should see a clear extension of the fuel enricher. Our example increased to 63mm when warm, an increase in length of 5mm. You will notice that the fuel enricher feels warm to the touch, this is normal.
8. If the enricher on your 50cc scooter seems to operate correctly then refit it to your scooter taking care not to damage the rubber seal. Use a tiny amount of grease to ease it back into the carburettor.