[Jjhart]

I have an older Honda 300 fourtrax, 2x4 always ran like a top, it had sat for a year or so. Bought a battery and fired it up, ran ok for awhile, now wen it’s warmed up it runs terrible, then quits, and won’t start. I have replaced the battery, carb, coil, and cid box, nothing has helped, any ideas?

 

[Mechanicmatt]

Did you drain the fuel tank and use new fuel before you fit the new carb?

 

[Jjhart]

Yes took the tank off and drained, and checked to make sure gas was flowing out

 

[Mechanicmatt]

Make sure your choke valve is seating properly. I would remove the plunger from the end of the cable set it back into the carb to see if it runs better.

 

[Jjhart]

Idles great until you try to drive it. Then it spits and sputters and won’t idle without holding the throttle open a bit. Wen It dies it usaly starts back up and idles fine

 

[Mechanicmatt]

Maybe test the ignition pulse generator.

 

[Goober]

When you don’t run these very often all number of things can go wrong. Corrosion. Rodent chewing, balky valves. So you probably can put the OEM parts back in it right and start back from jump?
Change plug?

download the service manual from the link in my signature block below. Use the oem parts finder at Rocky Mountain atv and Partzilla

 

[jwvanness]

I had a similar problem in a non-Honda engine, and it ended up being fragile gasket in the carb. I had just about given up trying to fix it, but it has been running great all summer with the new tiny, little, new gasket. The 15-year-old gasket must have dried out during the winter storage months. Good luck.