I've been searching all over for solutions to this problem. I have a 2006 Sportsman 450 that I can't get to run right. I bought the machine with a bad motor and replaced it with a used eBay one. It was said to be in good running condition. After putting it in, it fired up pretty quickly. The previous owner had installed a new Chinese carb. It wouldn't rev up much at that point. So I ordered a carb rebuild kit for the original carb that came with it, and went to rebuild it but the floats were cracked and I can't seem to find replacement oem ones. So I ordered another Chinese carb and rejected it with my new carb kit, except for the top jet under the diaphragm because it had a different thread size. Anyways, i put the carb back on and it still doesn't want to rev up all the time. It does always idle almost perfectly and starts great even when cold. It just bogs out some of the time when applying the gas, and won't rev up. It seems like if I give it a shot of carb cleaner in the intake, it will run great for at least a few minutes. Any ideas?