I've tried everything that I know how to do and I can't get my quad to stop shaking at idle. I'm just wondering if anyone has an idea why it would be shking. I can see that the handlebar moves fore an aft about a 1/4" and I've all ready got it as tight as possible.

 

My brother-in-law recently had the same problem with his 300 Express. It turns out that the front, top engine mount was either loose or broken. This caused an unusual amount of engine vibration. I would check all of the mounts and make sure they are tight. If this doesn't take care of it, let me know. I may have some other ideas.

 

If that is not it, lower the idle of the machine. I notice this on all polaris' and am not sure about other atvs such as honda, yamaha etc. but when you rev the machine up and it comes back down to and idle, righ before idle it hits a certain rpm and the handlebars shake pretty good. You might have the idle a little high.