I have a 2002 Bayou 300 2X4, with very low hours on it. Got on it one day, started fine, but would not run with the choke off. As I try to come off choke, it coughs and backfires both thru the carb and the exhaust pipe, then dies. Won't even come close to idling with the choke off. It actually runs well with the choke on, no backfiring, no gagging or choking as you would expect, and idles fine. Checked the choke slide/adjustment, and all looks good. Took the carb apart about 5 times to clean/clear the jets and inspect, looking for something, anything, but everything looks fine (Keihin CVK32 Carb, with vacuum piston and bystarter choke system - no butterfly). I also replaced the spark plug, which was black (but I don't think that was a good indicator because I've been running it with the choke on). Nothing has made any difference, still the same symptons...no worse, no better.
Has anyone had similar problems, or any advice to offer? I DO NOT want to bring it to a dealer, but I may have no choice if I don't come up with something else to look for.[img]i/expressions/face-icon-small-disgusted.gif[/img]

 

Man that sounds like its starving for fuel when the choke is off. check all lines from the tank and drain and clean the tank. You might find some junk built up around the bottom of your tank thats clogging it up. Your fuel petcock could be clogged up or even jammed up. I had to have mine replaced for the opposite reason, it wouldnt shut off. You can bypass it for a test to make sure. then make sure your gas cap is venting, maybe try running it without it. Make sure any vent lines going to the carb are not clogged. Hope you find it, I would hate for you to have to take it to a dealer...

 

The pilot jet is plugged. Its the smallest passage in the carb, and is the first to plug. By using the 'choke' which is actually an enrichener, allows enough gas to let it run, and when you close it off, the pilot wont supply enough to keep it running.
When you take it apart, remove the pilot jet, and run a strand of 22 gauge stranded wire, thru it. If you cant see light thru it, like looking down a straw, then toss it and get a new one.
Start the mixture screw at 2 turns out from lightly seated, and adjust from there.
One way to keep this from happening again, is to turn the gas valve to off, and either run the motor til the float bowl emptys and it dies, or drain the float bowl, ..if you know it wont be started for more than a week. Its the constant evaporation, and refilling of the float bowl that leaves deposits in the small passageways of the carb.

 

Hmm- leaving a carb dry like that will predispose the carb to water build up (condensation) for lack of gas, then you'll really have some trouble. I've alawys left the quad over the few winter months with gas in the tank with no ill effects. Definitley sounds like a clogged jet in there, newdude. 400PrarieXLT just about hit the nail on the head.

 

yOUR CARB DEFINITELY NEEDS TO BE CLEANED. LEAVING GAS IN THE TANK IS FINE BUT IF YOU ARE GOING TO LEAVE THE QUAD SIT FOR A LONG TIME DEFINITELY RUN THE FLOAT BOWL DRY. TRUST ME ON THIS ONE I DEAL WITH CARBS ON BOAT MOTORS ON A DAY TO DAY BASIS AND IF ANY CARB IS SUSCEPTIBLE TO MOISTURE IT IS A BOAT CARB. RUNNING THE FLOAT BOWL EMPTY OR DRAINING THE BOWL WILL HELP TO KEEP THIS FOM HAPPENING AGAIN. ALSO IF YOU ARE NOT GOING TO RIDE FOR A WHILE THEN PUT FUEL STABILIZER IN THE GAS WHILE YOU ARE STILL RIDING. THIS WILL FIGHT THE GUMMING UP OF YOUR CARBS SO YOU CAN HAVE YEARS FULL OF HAPPY RIDING.

BRIAN

 

I absolutely agree I'm starving the engine, but I don't think its the fuel feed into the carb. I pulled the hose from the tank valve, and I'm getting excellent flow from the valve in both the reserve and normal valve positions.

 

Your carb needs to be cleaned. You can take the hose coming from the tank and you will still get fuel to the carb. If your jets are clogged then no matter how much fuel is coming from the tank the thing won't run unless the choke is on. You eliminated the tank so now focus on cleaning your carb and see where that gets you.

 

Thanks for all the help from you guys. I found the problem. As stupid as this seems, it was a low float level, and I caused it. I believe the original problem was a clogged pilot jet, just as HONDABUSTER said, but I probably cleared it when I cleaned the carb the first time. After initial reassembly, the carb was leaking thru the overflow, so I took it apart again, cleaned the needle valve, then put it back together. Still had overflow, so I took it apart again, and lowered the float level...apparently too far. Today I readjusted the float, using methods/numbers from CLYMER'S Repair Manual, and its running excellent. Two lessons learned: 1) Low float level will lead to the exact same symptons as a clogged pilot, 2) don't ever mess with float level unless absolutely necessarry!!
Thanks again![img]i/expressions/face-icon-small-smile.gif[/img]

 

Do u have procedure for adjusting float level?