I thought you Raptor owners might be interested in another quad that has dual carbs. My quad has a highly modified 350X motor that has dual 34mm Keihin carbs. The intake was machined to expose both intake ports and then a custom aluminum manifold was made so each carb feeds one valve.

Click on the photo page in my signature and look on the "my quad photos" page if you are interested in pictures of the dual carb setup. I am happy with the performance of this setup but I sometimes wonder how it would compare to one larger single carb. I believe the largest advantage with two smaller carbs is throttle response and low-end power because this motor is absolutely incredible down low. I can crack the throttle just off idle up to 4th gear and it will light up the tires on any terrain including dirt, grass, and pavement! There is never any bog or hesitation even when in too high of a gear.

I may be able to help with any carb tuning questions since I have raced this setup for a few years. I do think the jetting on the Raptor may be more tricky since one carb feeds two valves and the other only feeds one. My head only has two valves so both carbs have the same size main jet (but not the same size needles).