Quad not running smoothly...

I recently moved my ATV from Pennsylvania (low elevation) to Denver (high elevation). As soon as I took it off the truck, it wouldn't stay running. It runs if I give it a little gas, but as soon as I let off the throttle, it stalls out and dies. It ran fine in PA. Think it could be because of the thinner air? Where do I start with fixing it?

Thanks!

Welcome to the site and Denver. My wife and I live out near the airport. For every 1000ft. you went up in elevation, go down 1 main jet size. that will get you set.

I would love to meet up for some riding.