Gregory Bender

Carburetor balancing/synchronizing without carb sticks

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models



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Even if you don't have mercury carb sticks, you can still do a pretty good job of synchronizing the carbs by hand (both of the following methods are performed with the engine off). And, since the factory didn't include bosses in the intake manifolds to which mercury carb stick could be attached, they expected (and provided explicit instructions in the manual) the carbs to be synced without them.

The factory recommendation

One method (recommended by the factory) is to put a thumb and a finger into each air inlet and feel when each slider starts to move when you very slowly open the throttle. The goal is to make both sliders open at exactly the same time.

John Schwartz's technique

An easier and more sensitive method is to create two 6 inch straight pieces of wire. Place each wire in the air inlet with the end under the slider. The other end of each wire should come pretty close to meeting in the middle. Now, when you open the slider very slowly, you can simply view which wire moves first.

Charlie Mullendore's technique

Contributed by Charlie Mullendore of Antietam Classic Cycle on the Yahoo! Loopframe_Guzzi news group.

When there are no vacuum ports, I use drill bits of different sizes to synchronize the carbs.

  • The air filter(s) will need to be removed.
  • Engine not running.
  • Pick a drill bit from your set that will just fit between the bottom of the carb throat and the bottom of the slide with the throttle released. Try the same bit on the other carb - if it won't slip in under the slide, adjust the (knurled) idle screw in until it does - if the bit fits too loosely, then adjust the idle screw out until it fits the same as the other carb.
  • Now open the throttle slightly and use the friction screw on the twist grip or other means to hold it there. Use a larger drill bit in the same manner as before to measure the opening height of the slides. If one is higher/lower than the other, use the cable adjuster on the top of the carb to adjust the slide up or down as needed.
  • You may have to use the idle screws to adjust the idle speed up or down after this, just make sure you turn them the same amount.
  • This will never be as accurate as syncing with a vacuum manometer.