My '93 TRX 300 is backfiring alot lately. It does it when I let off the throttle and if I gear down to slow down. Any idea as to what could be causing this. I thought that maybe the carb needed adjusting but I could'nt find the air/fuel mixture screws. Where are they located? Any information would be great.

 

Backfiring on let off, indicates a lean condition in the idle circuit. Either you have an exhaust leak, intake leak, or the mixture screw is lean.
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Its number 6 in this view. Its just forward of the float bowl, on the bottom of the carb.

 

Thanks for the info. Tried to adjust the mixture screw but of coures it was stuck and since it was a brass screw it is now ruined. Don't seem to have any intake or exhaust leeks that I can find. (Any ways to check for them that I could try to be sure?) I know the spark plug is old, could this cause it? I changed it once but when I put in the recomended plug, the bike would die out once it heated up. The recomended plug is DPR8EA9, but the plug in it is a DPR7EA9. I havent been able to find a replacement one of these ones yet so just put the old plug back in.

 

the drp7ea is a hotter plug meaning that the bike may start easier out in the cold but it will also make the bike run a tad bit warmer. i would find a stock one if it was me unless the weather is really really cold. our local dealers have them here.


yes, i would think you just need to turn the fuel screw counter clockwise a little bit. if that little bronze screw was stuck, there is some problems. it should move without much trouble.