Hi I have a 03 grizzly 660 just rebuilt the carb and put new spark plug in. Wheeler starts and idles great. When I give it 1/4 throttle it spits and sputters but when I give it more gas it is fine. Does it in park and all other gears. Has fresh gas in it. Not sure what it could be. Any help would be great. I ordered a new carb hoping that fixes the issues. I’m guessing it’s getting to much fuel cause if I turn the fuel off and it starts to run dry it revs fine till the fuel is gone. Just wondering if anyone has any tips

 

The spluttering as it goes from idle jet onto the main is usually a blockage in the idle jet, but as you have found it runs better as the float level goes down, maybe not a blockage, but the jet needle adjusted wrong? If I remember rightly, the float needle is a strange device on that model, with an O ring round the seat, which has to come out when you take the float bowl off, not sure if it is possible to get the float level wrong on that carb, but that is another possibility if it is. I would put the old spark plug back in just in case the new one is faulty, but would guess it is fitting a new carb that will cure it. Another thing you have to check on Yams is a cracked inlet manifold, because this is most likely to occur when you put pressure on it as you remove the carb.