My quarter-turn throttle with Webers was also very abrupt at small throttle openings like up to 1/8 throttle, so I reshaped the cam to make it more progressive, with a smaller diameter at the first part of the travel. I cut it using two hacksaw blades in the holder to give a wide enough groove for the cable. It added maybe 1/8 turn to full travel, but is more civilized on the street.