5-28 FUEL SYSTEM AND THROTTLE BODY • Connect a tachometer. • Start up the engine and keep it running at 1 150 r/min by turn- ing throttle stop screw 3.  Avoid dirt drown into the throttle body while running the engine without air cleaner box. Dirt drawn into the engine will damage the internal engine parts. • Turn the air screw 4 of the gauge so that the vacuum acting on the tube of that hose will bring the steel ball 5 in the tube to the center line 6. NOTE: The vacuum gauge is positioned approx. 30° from the horizontal level. • After making sure that the steel ball stays steady at the center E line, disconnect the hose from the #1 throttle body vacuum nipple and connect the next hose to this vacuum nipple. L • Turn air screw to bring the other steel ball 7 to the center line. P • Repeat the above process on the third and fourth hoses. M The balancer gauge is now ready for use in balancing the throt- tle valves. SA Throttle valve synchronization Using the vacuum balancer gauge, inspect the throttle valve synchronization in the same manner as the digital vacuum tester. Pay attention to the following points: The vacuum gauge is positioned approx. 30° from the horizontal level, and in this position the four balls should be within one ball 30˚ dia. If the difference is larger than one ball, turn the balance adjusting screw on the throttle body and bring the ball to the same level. A correctly adjusted throttle valve synchronization has the balls in the #1 through #4 at the same level. 09913-13121: Vacuum balancer gauge NOTE: * During balancing the throttle valves, always set the engine rpm at 1 150 r/min, using throttle stop screw. * After balancing the four valves, set the idle rpm to 1 150 r/min by the throttle stop screw.