Engine will only run on full choke, stalls on no choke.. bad carb..???

Okay well this question isn't for my TE450, but instead for my 1996 Yamaha Kodiak 4x4 ATV 400cc. I am asking it here becasue the knowledge of you guys I know is great and I bet you could give me some answers..

anyhow here is my problem...

last year I had to put a new main jet in the carb on this atv becasue it wasn't running right, it would bog down and stall everytime I gave it more than 25% throttle. So I opened the carb up to find that the main jet was broken in half. So last year I put a new main jet in, new battery, changed the oil, did some other stuff and the quad was running great! Well I ONLY use this quad for plowing my driveway so I keep it stored in my shed all spring, summer and fall.

So anyhow, I take it out of the shed the other day to get the plow on and find that the quad didn't want to idle with no choke. It was running sorta weird like backfiring and stuff even with the choke on so I thought maybe I had bad gas from the gas sitting in there all year. So I siphoned out all the gas and put new fresh 93 octane gas in it. I then started it, and on full choke it would idle fine (idle fast that is but that's normal on full choke). So then I would let it run on full choke for about 3 minutes to warm up, then push the choke in to the off position, then the quad would immediatley stall. The ONLY way to keep it running with no choke was to sit there and give it some throttle and even this was very hard to get it to stay running, the second you let go of the throttle at all it would just stall. But then if you put full choke on again it would idle fine (fast idle on full choke). So basically it WILL NOT run without full choke, and even with full choke on I still can't ride the thing because as soon as you give it throttle with full choke on it will stall, I guess it gets flooded with gas.

Another thing I noticed is that when the quad was off, and the gas line was on, that gas was dripping out of the carb overflow tube onto the ground. It was almost like something inside the carb is stuck open so the gas is just flowing through the carb and out of the overflow carb line onto the ground. So I took a screwdriver and hit the side of the carb a few times to see if something was stuck inside the carb causing this gas leakage and after wacking it a few time the gas stopped running out of the overflow tube. So once I stopped the gas from coming out, I tried starting the quad again, same thing, would only idle on full choke.

So the weirdest thing to me is the fact that it was running perfectly at the end of the last winter before I put it in my shed. Now this year I start her up and it won't run, so I think there might be something messed up with the carb again, although I don't know how that could be being I didn't ride this quad all spring, summer and fall..

any help you guys can give? do I need a new carb? or do they make some sort of a carb cleaning fluid I can put in the gas tank and run the quad, will this fix this issue possibily?

thanks again!

if it had old gas sitting in the float bowl for a long time it may have gunked up a number of things in the carb. The first thing to do would be to replace the pilot jet, or at least clean it. They typically have very small orifices and are prone to being plugged up. The pilot jet essentially controls the flow of fuel in the closed throttle through the early stages of throttle opening. If it is clogged it can cause a situation like you describe. This may just solve your problem without too much screwing around. Often you can get to these by simply removing the plug on the bottom of the float bowl. Many carbs have acces to both the main and the pilot through this hole. You should be able to remove the pilot with a small flat blade screwdriver. I am not familiar with your quad but often you can just loosen the clamps and rotate the carb enough to allow access / visibility.

Further, the fuel coming out of the overflow tubes indicates something caught in the needle/seat that regulates the amount of fuel in the float bowl. The fact that there is crap in there would make me even more suspicious of the pilot. That being said there could be other passages in the carb that may be clogged so it couldn't hurt to pull the float bowl, and clean all the passages especially the one that the fuel screw regulates.

how do you clean the jet? is there something I can spray in there for cleaning it, sorta like a gum out or something?

how do you clean the jet? is there something I can spray in there for cleaning it, sorta like a gum out or something?

This is what can happen with older fuel in small engines (not car/truck) as I described in your other thread...

Your float valve area of the carb & pilot jet are gummed up - no there is no damage but you it would be good to remove the carb and clean everything. Chem-12 or other type of cleaner works well enough, possibly in conjunction with a small wire like a strand of guitar string or electrical wire.

Personally I don't spray carb cleaner everywhere but focus on the orifices that need cleaning.

Stabil works awesome for us and we use it for everything except the cars/trucks year round and have had no issues since doing so. Sea foam is another product that people seem to like but have not tried it because stabil worked for us.

We had huge issues with our trail bikes with CV carbs like the one on your atv until we used stabil - the lawnmower, leaf blower, etc also run much better.


Take a strand of cable( steel) like form an old brake cable or something and use that to go into the pilot as well as spray it..that pesky thing is notorious for clogging up. When I am done riding my bike I run it out of gas to prevent as much of this as possible..some compressed air will help too.. and while you at it for safety sakes throw an inline gas filter on toprevent any other little particles from clogging up mr pilot jet...

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