i think the 05's are worst then the 07's on the 750 as my friend hasnt had no where near the problem w/ the new one back firing. i know @ one time the dealer put bigger jets in the front cyclinder ( i think) and it helped alot.

 

It actually sounds like a possible "sticky" valve issue. However, being that it's so new, I'd be leary to think it is. (although I've seen that be the fix for quads owned for less than a year.) Course, if it was a valve issue, the problem would go away as the engine warmed up. (unless they're really otta wack)

I would check all of your vacuum hoses. The symptoms sound like the issue my buddy had this weekend. We were running thru some deep stuff, and one of his hoses sucked up some junk. It idled crappy, and coughed and sputtered with full and half throttle...

good luck...