BYING FZR 600 AND FITTING THEM ON YOUR 400 IT´S A BIG WRONG. REQUIREMENTS OF YOUR 400 ARE COMPLETELY OUT OF THESE OF 600. YOU´LL SIMPLY HAVE A FUEL CONSUMPTION AND NOTHING MORE. YOU ´LL ALSO HAVE TO KNOW THAT YOUR CARBS ARE 30MM AND 600´S ARE 32MM. ALTHOUGH YOU ´LL HAVE NO FITTING PROBLEMS, YOU´LL HAVE PROBLEMS ON THE LOW RPM TORQUE. THE BEST SOLUTION WIIL BE A CARBURATOR KIT (GENUINE OR AFTER MARKET)