Reply To: GT250 EFI Throttle Body Synchronization
Update:
I connected the manometer directly to the throttle bodies and started it up. Rear TB was pulling more than the front, which meant that it had a stronger vacuum from the motor and needed more air, so I slowly opened up that TB butterfly until both cylinders matched. It idled at 2100 rpm. So I turned each throttle body down one by one until the idle sat at 1400rpm and it idled very well with both cylinders pulling same vacuum. Here, the idle stopper is set!
Moving onto on-throttle settings, the front TB was pulling more vacuum under throttle (needed more air), so I had to increase the tension on this cable until both TBs responded equally to throttle being pulled. Engine pulled equal vacuum (or close to equal) at idle and on-throttle now, so the cable tension is set!
Now I re-route the vacuum lines back into the ISC and re-introduce it into the air system. Bike starts up right away, idle settles down at 1500-1600, revs freely and seems happy.
Note: If your TBs are set from the factory, do not mess with them! If its already too late and the damage has been done, this method should get you 99% close to it. Use a good quality manometer and a cold pint of your favourite beer, have fun with it. Good luck!