I recently took an 883 engine and replaced the cylinders with 1200cc, used buell heads, an andrews n-4 cam with adjustable pushrods and crane roller rockers. The intake system used is a Rivera dual plenum forward tilt with dual Mikuni 42mm's attached. The first setup never worked right first due to holes in the plenum forging and then due to a defective carburetor. The replacement setup has turned this setup into a rocket sled, but the thing will not run at mid range. It goes very rich at around 3500 rpm and will not lean out until around 4100 rpm at which point you better be holding on tight! We have tried every possible jet combo. Does anyone have a suggestion?