MOPED ARMY

The generally accepted theory we have about mopeds that suddenly start four stroking after running for a while is that fuel mix is getting kicked back into the air filter through the carburetor. After a while, the filter becomes so saturated that it begins blocking the air flow (thus enriching the fuel/air mixture). Too much fuel results in four stroking. Taking the air box off will not make your moped work better because your engine requires the resistance the airbox creates --indeed many people find their top speed <i>drops</i> when they remove their airbox.

You didn't mention what kind of moped you ride, but PA-50's are notorious for four stroking at top speed. If you let us know a little more about what you ride, and what conditions caused the four stroking (i.e. how long you were riding, what kind of fuel mix, etc.) we might be able to tell you how to fix the problem.

To figure out your average speed (in mph) take the distance you travelled (in miles), and divide it by how long it took (in hours --e.g. number of minutes divided by 60). You said it was 30 miles one way and that it took you 50 minutes. This would work out to 30 miles / 0.83 hours = 36 mph.

Chris.

i have a tomos targa. i took my air box out because it would four stroke. the point is that the engine started popping. the day before i left i took the bikes cylinder off and cleaned everything up. one thing that i noticed was that there was a lot of carbon on the head and the pison and the exaust port had a lil more that the last time i cleaned it. all these parts had no carbon on then before i advanced the timing. could this be the reason for the carbon? and another thing... the piston had a brown is yellow kinda color on it. this color was found right after the rings and in the middle of the rings. does this mena my rings are dead? or could this be because i put a new piston in it and the new piston/ rings dont match my cylinder exactly. the cylinder had no scratches along with the piston.could the new piston be the reason for the popping? any more feedback.

-mike

Hi! If you don't solve it with what you've tried so far,try replacing the spark plug with one that's one heat range lower.At that high an r. p. m. ,the spark plug can get hot enough to predetonate the mixture,causing a slight backfire or popping.BYE!