7. Slowly unscrew the stop screw (2) until the speed is between : - 550 and 600 r.p.m. (vehicles —»| 9/ 1968) - 625 and 675 r.p.m. (vehicles }—™ 9/ 1968) Ensure that the H.P. pump does not charge while the tachometer is being read. 8. If the running is erratic, re-adjust the mixture screw (3) (do this very slowly). NOTE : After each adjustment on the secondary butterfly adjusting screw (2) flip the throttle open slightly, with the manual clutch control in the engaged position, to ensure that the butter - fly returns fully to the stop screw.