Re: [T3] Syncing dual weber carbs.

[Nathan Jacobsen <jacobsen@foxinternet.net>]

Synchronizing dual carburators is virtually the same process regardless of
the make or model. In order for this to be successful, you must have the
valves properly adjusted, ignition properly adjusted, no manifold vaccuum
leaks, and the right carburator jetting to match the engine configuration
(displacement, cam profile, etc.).

1. Disconnect linkage so that the idle adjustments on one carb will not
interfere with the opposing carb.

Bonus question response: The reason you must disconnect both carbs is so
that the throttle mechanism will not interfere with the idle speed
adjustments (see #6). Even if you have received advice on other dual carb
setups to only disconnect one side, you must check to make sure the linkage
does not interfere with your ability to adjust the idle screw on either side.

2. Start the engine and let it warm up.

3. Adjust idle mixture screws one carb at a time. Screw it out until the
engine slows down (rich mixture). Screw it in until the engine slows down
(lean mixture). If nothing happens when you screw it in or out, the idle
jet is probably blocked with dirt. Screw it back out until the engine
speeds up, then about 1/4 more turn. Do the same on the other side.

4. Hook up your uni-syn or other vaccuum guage to the top of the carb(s)
and adjust the idle speed adjusting screws one side at a time, so that the
guage shows each carb flowing equal volumes of air at the proper RPM.

5. Check the idle mixture screws again to make sure they are within the
proper range, as in #2. If any adjustments are made to the mixture screws,
repeat step #3.

6. Install and adjust linkage one carb at a time so that it pulls equally
on both carbs, and so that it allows the carbs to return to rest on their
idle speed adjusting screws. You may have to temporarily disconnect the
throttle cable, then reinstall after the linkage is adjusted, so that it
doesn't put tension on the linkage at idle.

7. Test drive. 

At 05:28 PM 9/3/98 +0100, you wrote:
>This is a contest to find out who knows the most about synchronizing and
>setting proper idle mixture on dual WEBER ICT 34s. The winner will receive
>my undying respect (woopee) and wide publicity as the PERSON WHO KNOWS
>THESE CARBURETORS (woopee).
>Not to mention it'll then be on the archive for good and no one will have
>to ask this again.
>Bonus points to answer this question: Why does Weber say to disconnect BOTH
>carbs from the linkage, when all other dual carb systems only have you
>disconnect one or the other?

Nathan Jacobsen
jacobsen@foxinternet.net

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