This atv had a broken cam sprocket. Installed new one set timing finally got it running. I have cleaned the carb 2-3 times to make sure it was nice and clean, but no matter what I do it still starts hard and will not throttle up.I can turn the idle screw up and it will run at a good high idle,but it just will not come up on the throttle it bogs down and just quits, then the only way it will start I have to lower the idle adjustment back down to a low idle. What could be wrong I have followed the service manual exactly. I checked the timing but the manual says that it will only if the timing marks are lined up there is no advance timing marks that I know of. What could be going wrong?