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Library Home Page > 2nd Generation (1999 to current) > Fuel System
Synchronizing the Carburetors
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Synchronizing the Carburetors

Revised by V-Dave

NOTE: Prior to synchronizing the carburetors, the valve clearance and the engine idling speed should be properly adjusted and the ignition timing should be checked.

1. Stand the motorcycle on a level surface. NOTE: Place the motorcycle on a suitable stand.

2. Remove vacuum plugs. (Fig.1)

3. Install:

  • Adapters
  • Vacuum gauge (Fig.2)
  • Engine tachometer (Fig.2) to the spark plug lead of cyl. #1.
    Vacuum gauge: YU-08030-A, 90890-03094
    Engine tachometer: YU-08036-A, 90890-03113

    4. Start the engine and let it warm up for several minutes.

    5. Check engine idling speed. If out of specification, adjust to 950 to 1050 RPM.
    Refer to "ADJUSTING THE ENGINE IDLING SPEED".

    6. Adjust carburetor synchronization.

  • A. (Fig.3) Synchronize carburetor #1 to carburetor #2 by turning the synchronizing screw (3) in either direction until both gauges read the same.
    NOTE: After each step, rev the engine two or three times, each time for less than a second, and check the synchronization again.
  • B. (Fig.4) Synchronize carburetor #4 to carburetor #3 by turning the synchronizing screw (2) in either direction until both gauges read the same.
    NOTE: Turning screw clockwise raises carburetor #4 and lowers carburetor #3.
  • C. (Fig.5) Synchronize carburetor #2 to carburetor #3 by turning the synchronizing screw (1) in either direction until both gauges read the same.
    NOTE: Turning screw clockwise raises carburetor #3 and lowers carburetor #2.
    Vacuum pressure at engine idling speed is 37 kPa (280 mmHg).
    NOTE: The difference in vacuum pressure between two carburetors should not exceed 1.33 kPa (10.0 mmHg, 0.4 inHg).

    7. Check engine idling speed. If out of specification, adjust.

    8. Stop the engine and remove the measuring equipment.

    9. Adjust:

  • Throttle cable free play Refer to "ADJUSTING THE THROTTLE CABLE FREE PLAY".
  • Throttle cable free play (at the flange of the throttle, grip) 4 - 6 mm (0.16 - 0.24 in)

    10. Install vacuum plugs.

    Location of Adjustment Screws

    Carbs 1 and 2 This screw is reached from the right side, but is located on the left bank.
    Carbs 3 and 4 The adjustment screw is the blurry part in the middle of the photograph.
    All carbs This screw is located behind the choke knob assembly on the left side of the bike.
    Here's a picture of the Motion Pro mercury sticks. The copper tubes are ballast tubes used to even out the vacuum pulses.
  • Last update: 04:55 PM Sunday, September 26, 2004

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