Gregory Bender

Carburetor - setting them up

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



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Thanks to Charlie Mullendore of Antietam Classic Cycle for providing the following information on the Yahoo! Loopframe_Guzzi news group. In Charlie's own words:

I don't use the old pull the plug wire off method to set the carbs. Here's the (likely a bit backasswards) way I do it instead:

If you don't have vacuum ports to hook some sort of balancing device to, you'll need to remove the airbox and sync. the carbs by measuring the height of the slides (from the bottom of the slide to the base of the carb throat). You can use drill bits or other similar objects as measuring tools.

As a base setting, I usually adjust the throttle stop screws (on the square area of the carb body) until there's an approx. 10 mm wide (semi-circular) opening showing at the front (towards the engine) of the slide when I look into the carb throat. Measure the slide height at the back (towards the filter) with a drill bit and set both carbs the same.

Make sure you have a little (3 mm or so) slack in the throttle cables where they go into the carb. top. If your throttle twist grip has a friction screw that you can turn in to hold the throttle open, turn it in to do just that. Or if not, figure some other means of holding the throttle open (assistant, duct tape, etc.). Open the throttle slightly and acting on the cable adjusters on the carbs tops, set both slides to the same height. Make sure you still have slack afterwards.

Turn the idle mixture screw (small screw, recessed into the carb body, near the float bowl)in until it seats lightly and then back the left one out 1 12 turns and the right one out 1 34 turns.

Release the throttle holding device, start the engine and let it warm up. If it's idling too high, turn each throttle stop screw out an eighth of a turn. If too low, turn them in an eighth of a turn each. Try to turn them in or out precisely the same amount to avoid disturbing the balance you set earlier. Next turn each idle mixture screw in until the engine speed drops (listen carefully as it can sometimes be difficult to tell) and then back it out 12 turn. If necessary, adjust the throttle stop screws again to achieve the desired idle speed.

Alrighty then. Clear as mud? Best job I can do right now with only 5 hours of sleep last night and after doing some sort of weird triathlon today (ride 4.5 hrs./200 miles to lunch in Keysville, VA, ride 5 hrs./210 miles home, push mow grass for an hour!).