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General Hints on Starting Engines
All moped engines operate on the same principles.  Every engine needs Compression, good fuel, and good spark to run. If your machine has been sitting for a long time, there are a few things you should check out before trying to start the engine.
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Technical Advice
1.  Check to see that the engine turns over, and has compression. To do this, remove the spark plug and try to turn the engine over with the starter. If it turns, make sure the kill switch is "off" so you do not get a shock from the coil wire, and put your finger over the spark plug hole firmly enough to get a good seal. Crank the engine over, and it should have enough compression to "pop" your finger off the hole.

 2.  With the plug attached to the coil wire, lay the plug against the block so that it is grounded. Turn the engine over with the kill switch on, and you should see a bright blue spark between the electrodes on the spark plug.

  3.  Look in the fuel tank. Check for sediment, or water pooled at the bottom of the tank. Water is heavier the gasoline, so any that is in the fuel will gather at the lowest part of the tank. A flashlight works well to see the bottom. If the fuel in the tank is more than a month or two old, it should be drained and replaced.
   In order for the engine to start, the good fuel must get into the carburetor. If your carburetor has a drain screw, open the screw and drain out the old fuel until you see the fresh fuel coming out.

  4. Turn the engine over while holding your hand about 2-3" from the exhaust tip. You should be able to feel air pressure coming out of the muffler every time the engine turns over, proving that the exhaust pipe is not plugged.

  5. Set the choke and turn the engine over. After several cranks, the engine should start, or at least start to "pop". If it acts like it wants to start, but will not keep going, turn the throttle to wide open and continue cranking. If it still does not go, reset the choke and try again.

  6. If the engine still does not start after several tries, remove the spark plug again to see if it is wet with oil, or fuel. If it is dry, make sure that fuel is getting into the carburetor from the fuel tank. You can do this by removing the fuel line from the fuel tank and turning on the gas valve. Fuel should flow out in a steady stream. If your machine has a vacuum operated fuel valve, locate the vacuum line on the fuel valve and remove it where it hooks to the intake manifold, then apply vacuum to it, either by using a vacuum pump, or by just sucking on it carefully. (make sure you are not sucking on the fuel line!) This will operate the valve, and fuel will flow out in a steady stream, as long as the vacuum is applied.

  7.  If you have removed the spark plug and it is wet, the spark plug may be fouled, or the fuel is not good enough to burn. If your spark plug is glossy black on the tip, it is fouled for sure, and cleaning will not help. The plug must be replaced.

  8. If your engine turns over well  a few times, then locks up, remove the spark plug and try to turn it over again. It is common for an engine that has been sitting for a long time to fill with oil in the crankcase causing a hydraulic lock. This will be obvious as the spark plug will have a drop of oil on the tip when you remove it, and oil will spurt out the plug hole when the engine is turned over quickly with the spark plug out. All this oil must be cleaned out before the engine will run, as the plug will be fouled with oil every time you turn it over. This is best accomplished by turning the moped upside down and cranking the engine repeatedly to expel all the oil. Do not force the engine to turn, as damage to the crankshaft may result.

  9.  If everything seems ok, but still no start, make sure that your throttle is working properly. On many mopeds the choke will not operate properly if the throttle is open. If the idle adjustment screw is in too far, it will act the same as turning the throttle, so the engine will not get enough fuel to start cold. Turn the throttle open, and let it snap shut. You should hear the throttle slide "click" down in the carburetor as it closes. This tells you that it is closing all the way, and is not being held open by a sticky throttle cable, or by being adjusted too tight.

  10. If you still are not getting fuel on the spark plug after choke is used, and you are sure the fuel is making it into the carburetor, remove the air cleaner boot from the back of the carburetor and place your hand over the end of the carburetor. When the engine is cranked over, you should feel your hand being sucked into the carb. It should also get wet with fuel. This will force choke the engine, and after doing this for a few cranks, the engine will draw fuel into itself. Then hold the throttle wide open, and crank again, to see if you get a "pop". If this method gives you a result, chances are pretty good that the carburetor needs to be cleaned out, as it will not flow fuel without a large amount of  vacuum. 

Scooter Therapy Inc
12 North Few Street  |  Madison, WI 53703    
toll free 1-800-411-1543  |  local 1-608-255-1520    

fax 1-608-255-1587  |  E-mail

Scooter Therapy Inc    

12 N. Few St   
Madison, WI 53703 

toll free 1-800-411-1543    
local 1-608-255-1520    
fax 1-608-255-1587    

Hours: M-F, 9-6 Saturday, 10-3  CST



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Scooter Therapy inc.

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