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Posted by: dumbjim Oct 11 2020, 12:24 PM

I have a 74 2l with dual weber 40 idf carbs. I took it upon myself to try and adjust them. I closed air bypass screws, turned the idle screw 1/2 turn in after initial contact, and backed out mixture screw one turn after lightly seating it. I also disconnected the linkage. I now can't get my car to start. What would be my next step? Thanks in advance.

Posted by: nditiz1 Oct 11 2020, 01:42 PM

You can screw the idle screws in further. The only thing that will do is increase your idle (make it faster). I can't remember the air bypass settings but those almost never need to be touched. They are used to keep each barrel on a single carb pulling the same.

Once you get it running. Adjust the carbs are pulling the same with the snail gauge using the idle speed adjusters. At the same time setting the correct idle ~1000rpm. Then you will move to the air/fuel screws. Slowy adjusting each barrel by listening and getting the fastest idle. Too much either way it will stumble so find the happy middle.

Posted by: Red76 Oct 11 2020, 01:45 PM

Jim,
No offense intended here but what you have written so far seems like maybe a typo. If its all correct you should first reset the carbs to where they were when you started. (Undo what you did). Then try to start the car. If that works then maybe you can find a YouTube video that explains how to synchronize your carbs.
Good luck!

Posted by: Gint Oct 11 2020, 03:00 PM

Have a look at Perry's sync how to on post 12 of this thread: http://www.914world.com/bbs2/index.php?s=&showtopic=348949&view=findpost&p=2855310

Posted by: michael7810 Oct 11 2020, 05:50 PM

I should run with your base settings. Maybe with the linkage disconnected you’re not able to actuate the accelerator pumps to get it started?? Below is a pdf file with pretty good instructions for tuning Weber’s.
 Carb_Tuning.pdf ( 2.93mb ) Number of downloads: 47