300EX Backfires and dies

[James96GT]

My 300EX dies after riding for 45 min, 15 min kinda inconsistent. It starts to backfire and then the engine quits. It sometimes starts right back up, sometimes not. I checked the plug and it looks "normal" - dry, white electrode, and black by the threads. I just bought it so the plug could be new. I have a K&N w/pre-filter, lid off, HMF slip on ans a "jet kit"....bought it this way.... I cleaned the filter and drained and replaced the gas with fresh 93 Octane. Didn't seem to help. I must say since it's loud right now (pipe) I am taking it easy keeping the throttle low and only making it as high as 3rd gear. Am I overheating? Bad ignition coil? I'm new to the ATV arena but have some mechanical know how...

[James96GT]

Spoke to a co-worker and he says to jet the petcock fuel filter/screen. Sounds like a fuel delivery issue since the plug looks "normal"..... that make sense?

[87redrider]

Originally posted by James96GT
Spoke to a co-worker and he says to jet the petcock fuel filter/screen. Sounds like a fuel delivery issue since the plug looks "normal"..... that make sense?
Sounds like the perfect place to start. Remove the plastics above the tank, then remove the tank, the petcock unscrews, clean the screen in there. Maybe pull the carb and check the operation of the float if that doesn't appear to fix it.

[James96GT]

Thanks. Just finished cleaning the screen. Not too much debris but a little near the bottom. Cleaned the entire assembly. Re-installing the screen was a pain, mangled the reserve area a bit. May pick up a new one just in case. The outside of the carb is all gunked up so while I have it apart going to clean it up the possibly remove it and check it over.

Thanks again. I'll update once I get it up and running again.......

[87redrider]

Originally posted by James96GT
Thanks. Just finished cleaning the screen. Not too much debris but a little near the bottom. Cleaned the entire assembly. Re-installing the screen was a pain, mangled the reserve area a bit. May pick up a new one just in case. The outside of the carb is all gunked up so while I have it apart going to clean it up the possibly remove it and check it over.

Thanks again. I'll update once I get it up and running again.......
Alot of times, debris,(dirt,rust) settles in the bottoms of these metak tanks, pull the cap and look down inside, you'll prpbably see alot in there.

[James96GT]

I think I figured it out... I was one level below where I needed to be.... The Gas Tank breather hose was pinched off under the handle bar cover. The hose goes through the cover and through a larger protector hose and into the steering shaft. I was pinched off by the outer hose and frame! I had removed the carb and cleaned it all up filled the tank and took it for a ride... still stalled... on a hunch I check the hose and it was pinched and wedge pretty good... I took the gas cap off and the quad started and idled perfect. I haven't had time to ride it any longer but I think I am on to something especially since the tank was full for the first time when it started to die sooner. It will be great if that was all it was......

[87redrider]

Originally posted by James96GT
I think I figured it out... I was one level below where I needed to be.... The Gas Tank breather hose was pinched off under the handle bar cover. The hose goes through the cover and through a larger protector hose and into the steering shaft. I was pinched off by the outer hose and frame! I had removed the carb and cleaned it all up filled the tank and took it for a ride... still stalled... on a hunch I check the hose and it was pinched and wedge pretty good... I took the gas cap off and the quad started and idled perfect. I haven't had time to ride it any longer but I think I am on to something especially since the tank was full for the first time when it started to die sooner. It will be great if that was all it was......
Yeah that was gonna be my next solution. That vent hose is VERY important.:devil: