captainchaos

I may not be able to riddle it for you but I can share a similar experience (albeit on a different bike). My superhawks have never cared what I did as far as exhaust goes up to and including running around for a goof with no mufflers at all. I did have a tuned '99 gsxr600 (was a 600 supersport race bike I put back on the street) that would run perfect with an Akrapovic muffer on the Akrapovic header. When I tried a V&H SS2r muffler if immediately developed a HUGE flat spot midway through the rpm range. Swap back at it would disappear like magic. I'm sure someone on here a lot smarter can give you the exact reason why.

xeris

According to the Carb set up by 8541Hawk, fueling is lean off idle. Maybe removing the baffles makes it more so?

Butts

Thanks for the responses guys.

GaryG, not stock cans, allen key removable baffles for straight through! :-)

Chaos, that makes sense. However, its like I get the flat spot, but this power hit once over it. And I DO MEAN power hit, its like I've grabbed some extra torque and HP from mid onwards.

Caveat, my bike is NOT tuned, carbs are NOT synched, and I have no idea what my TPS is. I've never had a reason to, as with the baffles in it is a nice tractable power delivery and I'm happy.

rktdoc

Probably power has dropped off quite a bit in the slow speed area because you're way too lean (possibly even dropping a cylinder) then as you transition from the area of power curve covered by the slow speed circuit/ root diameter of the needle to the actual needle taper it richens up and your power curve feels as if the power jumps.
If you saw a dyno graph of the bike you could visually see this going on.

rktdoc

Probably power has dropped off quite a bit in the slow speed area because you're way too lean (possibly even dropping a cylinder) then as you transition from the area of power curve covered by the slow speed circuit/ root diameter of the needle to the actual needle taper it richens up and your power curve feels as if the power jumps.
If you saw a dyno graph of the bike you could visually see this going on.

apezman07

A better flowing exhaust will lean the mixture, so you will need to richen up the mixture. Start by turning the mixture screws out (richer) by a quarter or a half a turn and see what happens. You may need to turn them out several times at small increments in order to fine tune. Extreme measures would include re-jetting and shimming needles or installing a dynojet kit with adjustable needles.