Twin Weber Problems

[mcmurb]

9 hours ago, WhoIsSea10 said:

There’s a screw that can undone on the top of each carb which has a pinhole. Through the pinholes, I sync the butterflies of both carbs. Barely seeing them pass by if I shine a light through. After syncing, I adjust the idle screw accordingly. Even with a visual confirmation of both carbs being aligned, the vacuum being pulled by the front carb is higher than the rear. And still a rough idle. 

Yeah, I had the same thing.  I stuck a piece of thin wire down the progression holes and felt something so I thought the plate was where it should be.  It was only when I took the carb off and could look at it on the bench did I see that one of the plates was ajar preventing the throttle from fully closing.  Do you have the Weber manual yet?  It may make more sense to see the situation shown visually.  The difference from between fully closed and ajar is less than the thickness of the plate itself.

[WhoIsSea10]

5 hours ago, mcmurb said:

Yeah, I had the same thing.  I stuck a piece of thin wire down the progression holes and felt something so I thought the plate was where it should be.  It was only when I took the carb off and could look at it on the bench did I see that one of the plates was ajar preventing the throttle from fully closing.  Do you have the Weber manual yet?  It may make more sense to see the situation shown visually.  The difference from between fully closed and ajar is less than the thickness of the plate itself.

Yeah I think pulling the carb off and inspecting, might put this to rest

[scanner]

Have you checked progression holes of each carb are drilled in the same place? I bought a pair of Spanish Weber 151’s and they were not a matched pair, made good synchronising impossible.

[Hans]

Refresh my memory; did you try synching with idle below 1000 and reduced advance?

[WhoIsSea10]

On 10/11/2022 at 10:44 PM, scanner said:

Have you checked progression holes of each carb are drilled in the same place? I bought a pair of Spanish Weber 151’s and they were not a matched pair, made good synchronising impossible.

That never crossed my mind.

[WhoIsSea10]

On 10/12/2022 at 3:39 AM, Hans said:

Refresh my memory; did you try synching with idle below 1000 and reduced advance?

Havent tried it yet. Will open the hood this weekend and report back