Ive had other posts about this, but it got cold so i abondened my bayou untill spring, and now its starting to warm up and i dug it out and rode it some. heres my issue, i have straight pipe exhaust, which ill be switching eventually, a air filter that offers no restriction. ive never had this running without these mods. if i put it on full choke, it starts right up, no hesitation, it will stall out if i touch gas untill it warms up. once it warms up it will sputter every few minutes, than after maybe 10 to 15 mins of riding itll start sputtering bad, then itll quit, like flipping a switch(all with the choke on, if i take it off it idles way up then dies) I have a slightly larger main jet in it. stock pilot jet. cleaned and rebuilt carb a few times, and had it done professionally. my though was maybe it needs a bigger pilot jet? im not very good with carbs. thanks a lot!

 

Sounds like too lean condition at pilot circuit.

Stock pilot jet is #30. Try one size bigger at a time.

 

Check that the jets and carb passages clean, and check the float height too.

Also can check the plug wire and wire connections.

 

ive cleaned carb few times, and a new pilot jet is ten bucks, it is backfiring out of carb for the most part, exhaust sometimes. is it possible its a sticky valve? pardon my ignorance with four stroke. imma two stroke kinda guy.maybe low compression? i have yet to test that

 

well come to thing of it i adjusted the valve lash on it, and turned it over by hand with the covers off, and the valves appeared to move correctly

 

one more thing! it dosnt seem to have a whole lot of suction comming from the carb, not sure how much the little for stroke is supposed to have.

 

Do you have a service/repair manual?

Now it sounds like your cam timing is off. How did you check?

Instead of guessing on carb suction, measure the comrpession which should be 170-190 psi range at sea level.

What did you set the valve clearance at?
That also controls how much air would come in and affects how easy/difficult to start the engine.

 

valve timing is dead on, used timing marks on cam sprocket to check. at TDC. valve clearence set at intake .007in and exhaust at .008. you say 170-190 psi, thats piston compression right? i dont have a tester is the only reason i havent tested but maybe ill go buy one, ive needed on more than once. ill check timing again, ive also heard that the rocker/whole cam area wears on these things fast, and this little bugger has been worked hard through Mississippi mud. what wear should i be looking for? thanks you guys are much help

 

yes i do have service manual

 

My 300 Bayou only has around 130 psi and it works great. When I bought it, it was starting really hard, wouldn't run without the choke on and was running really hot and backfiring through the carburetor. It turned out that the previous owner had cut a bunch of holes in the airbox to help it breathe better and it was making it run too lean. I patched the airbox back up and the problems were gone. Too bad you don't have a proper airbox to try on it.
I also had the air vent on the gas cap blocked once causing it to stall out after a few minutes of driving.