I have a 2001 yzf 600r that I purchased new. The bike has about 27.000 miles on it. It bucks and surges real bad about 3500 rpm, but free revs just fine. It has a k&n air filter on it, and a scorpion exhaust pipe. I recently rejetted it with a dynojet kit, b/c the shop that worked on it drilled the jets instead of putting the kit they sold me in it. Still the problem exists. I have cleaned the carbs at least 3 times. The ignition coils test fine. I even tried a spare cdi box and have the same problem. I did take the bike down to be repainted but it was doing this before it was taken apart. I also replaced the notorious 2nd gear about a year ago. The tach also jumps around to 8000 rpm, and if im understanding correctly that has something to do with the fuel sending unit and not a run issue?

If anyone can help with this frustrating problem it would be much appreciated!!

Thanks,

Jeremy

your tacho bouncing at 8000rpm could be indicating a TPS fault.

If the tacho jumps up to 8000rpm for and then shows your normal revs then it is your fuel level sender that's causing it. (but not causing the bucking). When your low on fuel, left the tank and you will see the fuel level sensor is secured with 2 screws. Undo these and remove the sensor. It'll be dead easy to fix, a wire will have broken free and you just need to solder it back on ... you'll see where to easy enough.