KZ550 with GPZ engine strange sputtering...

Need to mention that between the airbox intake and the seat pan is only 3/4 of an Inch space because i run a custom seat...

Strange is in my opinion that i can full accelerate trough the gears and have no sputtering only when i almost close throttle and then whack it back open it is a little cough.
I got better but is still there.

accubond wrote: Airbox is stock.

Battery has 13.7 -14.0 Volts at 4000rpm

I dont know if i mesarued right at the coils (between Green and yellow/red and Black and yellow/red cable) there are only 5-6 V!!

Do i need new coils?

No, you did not measure the coil voltage correctly.
If each coil has a yellow/red wire on it, then measure from that wire to a ground point. A bare surface on the frame or the engine or frame ground bolt.

With mine, and a stock airbox, at 3211 ft altitude, I ran the stock #94 jets, and ran the needle in the middle position.

With pods, I ran #105 main jets, and left the needle in the middle.

I also modded the timing plate for 3 degrees more advance,

Good luck.

accubond wrote: Airbox is stock.

Battery has 13.7 -14.0 Volts at 4000rpm

I dont know if i mesarued right at the coils (between Green and yellow/red and Black and yellow/red cable) there are only 5-6 V!!

Do i need new coils?

Need full battery voltage to the existing coils.



Even a perfect brand new coil can't properly perform without full battery voltage being supplied to it.

Where voltage is being reduced somewhere between the battery and the coil, would check voltage at each connection in the wiring between the battery and the coil, starting at the connection closest to the battery.



And, as mentioned, full battery voltage to a perfect coil, may still be thwarted by too much resistance in the secondary circuit due to more than one component having resistance. Usually the one component having resistance is the plug cap, hence solid core non-suppression plug wires should be used, along with non-R spark plugs.

Good Fortune!

Seems that I solved the problem.

I lowered all fuel height levels a bit and no more sputtering.

I'd check the gas cap for air blockage too, this is something most riders forget; gas goes out, and air must go in for good flow. There should be screws holding the gas cap together, remove them, checking for blockage of the vent after dis-assembly.