Motorcycle Repair: stalling at midrange RPMs, yamaha r6, k n air filter

Question
eric,
i bought a 2002 yamaha r6 about 2 months ago. when i first bought it, you could barly hang on to the bike it was so fast. now it is having problems. when i get going seemingly reguardless of throttle position, the bike cuts out at about 10,000 RPM'S, in any gear uphill or down, 1/4 throttle or full throttle. here is a list of what is done on the bike; Akrapovic evolution full exhaust headers back, K&N air filter, carbs rejetted to allow more fuel, and i believe the sprockets have been knocked down a few teeth. any help that can be given would be greatly approciated. thanks!

respectively,
Leo Sterger

Answer
Leo,
sounds to me you are starving for fuel on the top end. check for air leaks around the intake area. make sure airbox is on tight. was the rejet done after the pipe install and did it run right then ? When it cuts out, is it a slow or abrupt cut and does it backfire thru the airbox when it does ? checking to make sure all clamps are tight and air box is on good is a good start. let me know about the questions i have asked, they are important.

Eric