I just bought a 2006 sunl utv, 250cc with a known no start problem. Got it home and have determined it is getting fire at the plug and fuel in the cylinder, but still will not start. I can take the plug out and turn the key and watch the fuel shooting into cylinder so I know its getting gas. When I crank it over with the spark plug in it sounds like a typical motor without spark. I have taken the plug out and held it to ground and turned key and you can easily see a strong, blue spark.

The frustrating part is if I dump a little fuel directly in the cylinder, put the plug back in, it will fire right up and run until the gas runs out. Is it not getting enough gas?? Like I mentioned, it is getting gas to the carb and I can see fuel spraying into the cylinder with the plug removed. I drained the fuel tank, put fresh gas in, put a new in- line fuel filter on and installed a new fuel pump. Any help would be greatly appreciated as I am new to atv/utvs with little knowledge.

Thanks

 

You have a fuel delivery problem obviously.

What do you mean by "[I] turn the key and watch the fuel shooting into cylinder"? It is dark in there. How could you see that? I'm confused. And with the plug out there is no pumping action. The piston just pushes air in and out of the gaping hole in the engine where the spark plug is supposed to be. So a cranking engine wouldn't suck in any fuel anyway.

You installed a new fuel pump? Fuel is gravity fed on every quad I've seen. I don't think there is a fuel pump.

Since you have a fuel problem the first place to start is with thoroughly cleaning the carburetor. That involves *complete* disassembly. Every screw removed, every jet removed, every passage checked for light shining through it. No shortcuts allowed here. For a primer I would watch several videos on motorcycle/atv carburetor cleaning on YouTube before beginning. They may not be for your specific carburetor, but you will get the basic idea.

 

I guess I wasn't real clear. It's not a quad that I have. It is a Side by Side or UTV vehicle from Sunl. I don't know if that makes a difference this is my first experience with any atv/utv.

It does have a fuel pump, it is not gravity fed. The carb sits higher than the fuel tank. After I replaced the fuel pump and removed the fuel feed line from the carb, and turned the key, it will pump out gas. So I know fuel is getting to the carb. To my knowledge of engines, fuel is mixed with air and sprayed in the the cylinder (via the carb through the intake) where it is ignited by the spark from the spark plug which causes combustion. When I have the plug out and turn the key I can see I fine mist of what presumably is fuel/air mix spraying in the cylinder as the engine cycles. It is dark but with the proper placed light you can see in. This is further demonstrated by dumping a little fuel down the cylinder through the spark plug hole, installing the spark plug, turning the key and the motor will run until the fuel runs out... maybe 5-7 seconds. I don't know the correct term, maybe its not called the "cylinder". Like I've mentioned, I have enough knowledge to be dangerous. But if I explained it right hopefully you get the idea of where I'm talking about. Its the port or hole the spark plug screws into.

I should state that last night I took the carb off and cleaned it. The main jet was plugged. I reinstalled everything back the exact way it came off and reinstalled on the engine. Low and behold it tried to start right off the bat which it has never done in the few days since I've owned it. Within the second try I got it to run for about a little over a minute although it was a very weak/low idle. It eventually died but I could get it to start consecutively after that but it would not stay running for more than a few seconds any time after that.

Clearly whatever it is, its either not getting enough fuel or not the right mix of fuel/air. With that said how do you adjust the fuel air mixture on a gy6 250cc carb? The carb has an electric choke, is there a way to test to see if it is working properly?

 

sometimes, one cleaning is not enough. you may need to purge the gasoline tank and lines. flush them, then flush/clean the carb and both jets again. heck, i've had to clean a carb 3x-6x before i got all of the "solids" out of the system. don't get discouraged. you're on the right track...........

 

I've not ever seen a UTV up close. I had ATV's stuck in my brain.

Fuel is mixed with air as the air is sucked into the engine. The engine is acting as a pump while it is cranking - pulling air in through the carburetor (and picking up gas), and pusing it out through the exhaust. With the spark plug out there is no significant pumping going on. I wonder if the fuel your seeing is left over in the cylinder from earlier.

Does your autochoke (bystarter valve) look like this?



If so see the trouble shooting chart under "Electric Choke Test" here:

Troubleshooting

Most of the time these things fail stuck in the "enrichen" mode. Thus you would not have trouble starting up the quad, but it would run progressively worse as the engine warms up and the choke failed to shut off.

Don't lose the little gasket behind the choke if you remove it.

You can see if you're not getting enough fuel in the air/fuel mixture by removing the air cleaner and choking the carb manually by partially blocking the air intake. This will increase the amount of fuel in the mix.

 

I had a chance to work on my machine again this weekend. I took the carb off again as suggested and cleaned everything thoroughly. After reinstallation it fired right up and idled for about 10min. As it hasn't ran in at least 6 months I just let it run for awhile. After about 10 minutes it was still idling but wasn't real smooth. I went to adjust the air/fuel mix screw, which on my gy6 carb is on the bottom of the throat on the intake side, a real PIA to get to. To my surprise the screw had vibrated loose and fell out on top of the starter. So after fishing the screw and the tentioner spring out I had to take the carb back off to reinstall. Got it put back together and it started right back up. After just a couple minutes of idling it died again. Tried to start and it wouldn't even fire. Thinking I adjusted the mix screw wrong, I went under to a make an adjustment and the damn screw and spring vibrated out again!!. Evidently the damn spring wore out and wasnt providing enough tention to hold the screw in place.

So I made a trip to the nearest atv shop (yamaha, suzuki dealer), and after a few minutes of listening to the parts guy tell me what a piece of crap the "chinese" brand is I finally twisted his arm enough and talked him in to helping me find the the closest comparable tentioner spring match from his stock of overpriced japanese parts. Paid $4.78 for a little 1/2" spring. The funny thing, he acted like he didn't even want to sell it to me knowing it would go into a chinese atv/utv!

Anyway, got it home, put it in, reinstalled the carb and it fired right up. Made a few adjustments based on the help from this site and got it purrin' like a kitten.

I wanted to say thanks for all the help and for all the invaluable information found on this site. If it wasn't for you all I'ld probably still be fighting with it!

 

glad you got it running. heck, i've learned something there myself about the spring you replaced. hmmmm...thanks....

 

Good on ya.
I have had numerous powersports, and right now have a Yamaha Warrior, and a Kawi Prairie(not to mention a Goldwing), and I was very leery when buying my 2 little Chinese (TAOTAO) ATV's.
I knew I would fall from the graces of the "big names", but felt this was the best intro into ATV's for the money. I was right, within an hour, my 2 little ones were off and running. My daughter's 110cc is flawless(except for daddy broke the chain), and my son's was until last night.
I went into this with an open mind, and the one thing that is a MUST, is that to own one, you need to be mechanically inclined.
A majority of the issues I have seen with these Chicom bikes is, starting issues.

It's great to see ya have yours all figured out. Now off to work on mine.