When riding (clutch out, going up a hill or lugging it...doesn't matter), it doesn't seem to do it. It happens when I stop and am just trying to get started again. If I give it a little gas it will just die. So I'll rev it and keep it revved while slowly letting the clutch out and it will STILL die. Also, while revving it to get started it will stumble and run badly even if it doesn't actually die. Once I'm moving and clutch is fully engaged, no problem. I was thinking pilot jet but it's almost as though I'm getting a bad spark, because when it dies, it's like I'm pushing the kill button. BTW, new platinum spark plug. Any ideas?