K75 Unable to synchronize cylinders

I'm stumped.
During the winter I removed the throttle body housing and plenum. The TB was thoroughly cleaned of gunk and bypass air screw's O-rings where replaced.
I am not able to synchronize the cylinders. (ie #1 cylinder reads high while #3 cylinder reads very low, while #2 is somewhere in the middle. The bypass screws can not make the adjustment, i have tried everything.)
A motorcycle tech well versed in k75 mentioned the butterfly valves are not matted from the factory from the through cleaning and debris removed plus 28 years of riding - 346,000kms.

Recommended to synchronize the butterfly valves before synchronizing the cylinders. He stated run k75 to operating temp
then adjust the idle screw to increase the RPM slightly above 950 RPM,
then close the bypass air screws and with a carb stick adjust the factory set TB screws to balance the valves which worked.
(I increased the factory set screw between #2 and #3 TB by 3/4 close wise turn.)

Next step to synchronize cylinders.
Opened air bypass screws 1 1/2 turns and with a little tweaking the cylinders were balanced, HOWEVER i can not return the 1200 RPM to 950.

Does anyone have information?

Bill,


It's usually a VERY bad idea to touch the linkage screws between the throttle bodies, but that is not helpful to you since you already did it. Note to others: DON'T TOUCH the screws on the linkage between the throttle bodies!!!

Are you sure the throttle position switch or the fast idle cable is not holding the throttle open? If not, just slowly tighten the bypass screws (while maintaining balance) until the idle is where you want it. Factory says 950 + or - 50. I prefer 1050. It makes for smoother takeoff from a light.