EZGO Backfiring on Low Throttle

rbdaves

rbdaves

Member
My ‘99 EZGO TXT runs fine when accelerating or traveling at mid-throttle and higher speeds. But when on low throttle and coasting it is backfiring. I have cleaned and adjusted the carburetor. I had the engine rebuilt by a well known rebuilder and there shouldn’t be any need to adjust valves or belts. A visual inspection of the throttle plate shows that, at rest, the plate is totally closed. Any help?
 
Is it running rich? Muffler has good baffles and not loud? By low throttle do you mean a slow speed where the throttle plates may be open?
 
Yes, Throttle plate is slightly open at slow speed. Don’t know how to answer your question on muffler. This gas engine is certainly loud compared to an electric cart.
 
I missed some important info on my original post:! This cart has a a Robin 295 cc engine. I installed a rebuilt engine but it took months to get it running due to unavailability of reliable parts. I finally was able to buy used OEM parts off a cart that was being junked.
 
So when you let up on gas pedal all the way the engine backfires? or Just when you are slowing down with slight pedal pressure?
 
There is a hill in the park that I stay at. As I slow to stop at the intersection, the backfiring starts. The the backfires continue as I slow down and come to a stop. At complete stop, the engine stops as do the backfires.
 
Here’s a little more to help with analyzing my backfiring problem:
I had a conversation today with a fellow that knows a lot about motorcycles and explained to me that the backfiring on minimal throttle can be caused by an engine that is running too lean. I remembered that there is an adjustment on the top of the carburetor that doesn’t have an adjustment screw inserted into it (see Picture). This adjustment can be used to adjust how much the throttle plate closes on minimum throttle. If, as my friend says, the problem has to do with a lean air/fuel mixture, this may solve the problem. I’ll be working on this tomorrow. In the meantime, is there any other way to adjust the air/fuel mixture on this Robin 295 cc engine?
 

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A backfire, as you describe, is usually caused by the the carb butterfly not coming to a complete close when the gas pedal microswitch cuts off the ignition.

Take the seat off, push the gas pedal, and watch the carb butterfly. There shouldn't be any movement in the carb butterfly and linkage until after the engine is cranking. Same as with the engine shutting down. Carb butterfly should be closed before the engine shuts off. This can be taken care of by adjusting the linkage.

Another cause of backfire could be. Is the linkage hanging up, or cable dragging in the housing, after running the cart at wide open throttle. Not allowing the carb butterfly to close soon enough before the ignition is shut off.

Also by the looks of the carb pic. Grab the carb butterfly by hand and see if it moves more to the closed position. I know the idle screw is gone but it looks like larger than normal gap between where the screw would be and where it would hit the idle stop pad on the carb. But this could just be me and my old eyes.
 
Classycarts: Thanks for that input. I put a Throttle plate adjustment Bolt into the carb and adjusted it so that the throttle plate doesn’t close completely. This appears to have solved the backfiring problem
 
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