Does it run without it?

 

Sure it runs, see: http://www.ablett.jp/bikes/vtr/air_box_lid.htm

But if you look at his dyno numbers on the last page, he gave up and went back to stock.

 

yes it runs pretty good but to me it fills like it could be jetted, thats why i ask i am used to 2 stroke motors on jet skis so i thought i would ask it runs pretty good but at idle you hit the throttle and it hesitates a little and get mild back fire some times at lower rpm but seems like there sould be a little more?

 

A lot more.. This motor should be strongest at the lower RPMs, with no need to rev it to get into it's powerband.

The airbox mod will move the powerband up to higher revs where this engine isn't suited to run.

Basically if you can't power wheelie in 1st & 2nd (strong runners even can do 3rd) it isn't running right. That doesn't mean it should wheelie every time you whack open the throttle, but it does mean if you want to wheelie you shouldn't have to rev it and dump the clutch.