I am working on a 2010 Sportsman 500 HO. This machine sat for two years because of charging issues so I changed the reg/rec and it began working as normal for three weeks. I never filled the tank up completely during that time, maybe halfway at most. One evening I filled it up completely and later found it had drained the entire tank out of the carb overflow at the bottom. There is a screw next to this hose but I'm not sure what it does.

I opened up the carburetor, sprayed it down with carb cleaner. I noticed the O-ring on the float was warped a little but I re-installed the carb and nothing different. I could start it up and drive it but it would leak gas when I stopped.

I then bought a cheap new carb instead of a carb kit. The new carb was the same except it didn't have the small o-ring inside the float bowl and instead had a metal cylinder shaped thing that wasn't attached to the float. The new carb didn't leak gas out of the overflow but the machine wouldn't start up by turning the key unless I pressed the throttle down on the handlebar at the same time. I could rev the engine high but it sounded sputtery when I did. As soon as I would let go of giving it gas, the RPM would gradually and quickly drop below 1000 and the engine would stop. Only one time did it idle and I drove it 100 feet and it stopped and then the same issue.

I decided to try the old carb again so I went out to buy an o-ring from the hardware store to see if the old carb would work if I replaced the worn O-ring on the float. The O-rings in the store were fatter so I wrapped it around a pencil and I stuck the pencil in a drill. I held a really fine dremel piece up to it until it shrunk to a size that would fit. I put the o-ring on the float and pressed down until it fit snug and wouldn't fall out. There is only one visible O-ring inside the float bowl and this is the one I'm talking about. I installed the carb again and the same problem persisted, except this time the fuel spilled out and I couldn't easily start the machine and the engine stopped easily; whereas, before I could drive it while leaking gas.

I feel like I'm at a dead end and think maybe I should buy another carburetor because the cheap one looked like metal had chipped off around the lip of the round part on top of the carb. The rubber that held the needle seemed to seal though because the metal was flat all around the circle. I think when the hot metal poured, it didn't cast fully because it didn't look chipped and maybe there is also issues with metal formation inside of the carburetor. Unless someone can identify soemthing from my description here and help me figure this out?

 

I had similar issue with gas leaking out of the overflow hose on carb. Turns out the float had a small cack and would fill with gas and kept the flow going. After replacing the float it's all good now.

 

I had similar issue with gas leaking out of the overflow hose on carb. Turns out the float had a small cack and would fill with gasand keel the flow going. After replathe float all good now.