Carburetors tune up

[CarlosSpider]

The matter is that I have already gotten tired of spending money in adjusting the carburetors of my Spider and I have decided to do it myself. For that, I have chosen this tool. www.carbtune.com.

The problem is synchronize the carburetors: I need to identify all the screws.


Twin solex sidedraft C40 ADDHE

These are the screws that I know

The 1 idle mixture screw
The 2 the idle speed screw
The 3 to synchronize the two carburetors
The 4 to connect the synchronizer (vacuum take off)

But what happens if the two barrels of each carburetor are not synchronized?
Which is the bypass screw that corrects this failure, and how it acts?

For what reason are the other screws? (numbers 5 and 6)

Thanks a lot.

[papajam]

To be honest, your pic was the first time I've seen a Solex equipped Alfa. But I've tinkered with a few Webers before and I'd think that the principles would be similar.
The carbs need to be syncronized to ensure that each pair of cylinders gets the same air/fuel mix. Symptoms of uneven mixture between pairs can include hard starting, poor/high/hunting idle, hesitation (flat spot), poor performance and high fuel consumption.
Before adjusting the carbs, make sure that the dwell, timing and idle speed are set to spec and the engine is warmed up. A word of caution. After the carb tool (manometer?) is hooked up, do NOT rev the engine. The resulting high vacuum on throttle closure will suck the liquid out of the tool and into the engine possibly resulting in engine damage.
With the tool hooked up and the engine idling, the height of the liquid in the front PAIR of tubes must be same as the rear PAIR. Ignore any differences in each tube for now. If the pair heights are not the same, slowly turn screw #3 until they are. You may need to readjust the idle speed at the same time. Once the pairs are equal, the carbs are synced.
Differences in the individual tube readings could be anything from a vacuum leak, bent throttle shaft/plate or carbon build up in the carb throat to a leaking valve, worn cam/follower or a valve that needs adjusting.
For the idle mixture, I turn each screw in, one at a time, until it's lightly seated. I also listen to the rpm drop. Slowly back out the screw until the highest rpm is reached, then turn it back in about 1/8 - 1/4 turn. The rpm drop for all cylinders should be the same.
Can't help with screws 5 or 6 (#5 looks like some sort of air bleed but it's open to atmosphere so not too likely) but perhaps someone more familiar with Solexes can.

[CarlosSpider]

Hello Papajam, thank you for your help.

The dangers of rev the engine with the “¿”vacuum gauge” = “vacuummeter”? I already knew them. It happened to a friend in his bike.

This synchronizer measures the vacuum but it doesn't use mercury, it uses stainless steel columns.

I attch a bigger pic of the carburetor.

[Santana]

hOLA cARLOS
could you tell me the year of your Spider???
yhanks

Ciro Italia

[CarlosSpider]

hello Santana

the year is 1981.

Today, I have identify all the screws.

My carbs are solex C40 ADDHE/20. Do you have information about it?

Regards

[jymz]

#5 pump jets
#6 idle air by-pass

If the by-pass screws have been messed with You'll need to close them completely (lightly seat). These are used to sync the carbs barrels together then you sync the two carbs together. You can check this with a vacuum tester on port #4. If the barrels are close do not adjust or close off the #6 screws.

[Santana]

The SOlex C40ADDHE were installed on the last version of the AR GT, year 1974 and are wer emission control type.
If you send me you address email i can send you some pic and some other information.
Ciao

Ciro

Quote:

Originally Posted by CarlosSpider hello Santana the year is 1981. Today, I have identify all the screws. My carbs are solex C40 ADDHE/20. Do you have information about it? Regards

[lazydays]

My 1986 Spider also has Solex C40s fitted and am trying to resolve poor starting problems - can someone let me know where I can find these pictures identifying the idle air bypass screws - the web references I have sound so far dont match properly my carbs


Dave

[Santana]

Sendm me an e-mail to ciro.guarino@atsf.it
i'll send you some information about the Solex .
bye

[CarlosSpider]

Quote:

Originally Posted by lazydays My 1986 Spider also has Solex C40s fitted and am trying to resolve poor starting problems - can someone let me know where I can find these pictures identifying the idle air bypass screws - the web references I have sound so far dont match properly my carbs Dave

[gt601]

I gave my Solex's away and installed Webers. WOW what a difference. Not to poke into this thread.

Paul

[lazydays]

Thanks - I have been considering switching them as they seem a bit tempremantal, however I wanted to just test how they were after I replaced the rubber mounts with solid aluminium ones - it is better than it was as the rubber was cracked and so leaking air making the mixture very weak