[Richard2]

1973 Belina 2L with Webers

It starts well and has lots of power, but the idle is unsteady and it takes 9 secs to drop from 3500rpm to 1000rpm. The throttle linkage is free and returns to the rest position immediately. I had the distributor out. The springs and weights are free and operate smoothly. The inside of the distributor is clean and rust free. I've got the idle adjustment screws out 1.5 turns. I've had them upto 3 turns out. It runs very roughly there, but is still very slow returning to idle when throttle is released.

I've been into the carbs for cleaning, per this thread:
http://www.alfabb.com/bb/forums/showthread.php?t=38518&highlight=richard2

What am I missing? Would float adjustment cause a slow return to idle?

 

[Bertonemorten]

What about carburettor syncronisation, is it correct ? My 1300 had the same symptoms because the syncronisation was bad. Now it returns to idle very smooth and fast. You can check the idle mixture with colourtune, its cheap and easy to use.

 

[acurtiss]

Yes, sync the carbs and this problem should go away. Basically one carb is running 'faster' than the other so it's keeping the revs from dropping as quickly. Also check for vacuum leaks and be sure the timing is correct.

Syncing the carbs can be done in a million ways, but I ended up forking out the $$ for a airflow meter and adapter for the dcoe/sidedraft. Even with the right tools it seems to be more art than science.

BTW, I thought colortune was more for adjusting idle mixture than carb sync? I can see how it might help in diagnosing sync probs, but it doesn't seem like that would be as accurate as an airflow meter (unisys or whatever).

 

[Richard2]

So if I adjust the the screw that connects the carbs so that the idle drops, that would be in the right direction?

 

[acurtiss]

Do you have the Alfa Owners Bible or another basic guide on carb work? It's not quite as simple as listening for an idle drop, although in your case that *might* be the right direction. Really what you need to check is air flow through the carbs. This is usually done with a Unisys or similar tool (google it and you'll see plenty of descriptions). When air flow through both carbs is the same at a given rpm, your carbs are in sync.

The adjuster you're talking about is what controls where the two throttles are in relation to the (one) pedal input, and is what you'll adjust to sync the carbs.

 

[Gary Williams]

There's a link on this page to one of the best Weber how-to websites around:
http://greend.com/carb_software.htm .