Solex 2bbl post rebuild setup

[7sis]

Hi I'm looking for help for setup my carb which I reinstalled post rebuilding it... It was due since it seemed to still have the original gaskets in!

 

Anyways, carb is now back in place however engine doesn't idle... I need to floor it to start and hold the gas pedal about 50% to have a rough 2000-3000 rpm to keep it running... 

 

I attached a video for an example

 

I searched to forum quite a bit but couldn't find much info on the solex 2bbl for this sort of issue... I'm quite a newb and haven't played much with carb since I got the carb...

 

My car is a 1975 all stock 

 

Any help would be appreciated! Thanks!!

 

 

[Buckeye]

There was recent discussion on Solex. Check out documents provided in my post.

 

 

['76mintgrün'02]

This is probably in Buckeye's link, but one thing to check is to make sure the idle cut off solenoid in your photo is getting 12v with the key on and that it makes a clicking noise if you pull off and replace that wire (with the key on).  If the wire has power, but you don't hear clicking it could be a faulty solenoid, or sticking, or something.  It won't idle if that is not working.

[Mike Self]

If your idle problems are primarily when the engine's cold, but OK when warmed up, it's probably the choke.  Those Solex automatic chokes were problematical when they were only 5-6 years old: the fast idle cam wore to the point where the idle wouldn't stay at it's higher rpm while the choke was still engaged because the ratchet teeth wore.   

 

That was the primary reason that I bought a manual choke Weber for my '73 about 1980/81 to replace the Solex:  no fast idle when cold.  I even hand-filed a new fast idle cam, but to no avail.  At the time a new choke assembly for the Solex was $85 and a complete manual choke Weber was $92--not a difficult decision!

 

If your idle problems are also when the engine is warm, make sure you didn't accidentally swap idle jets between barrels, and as was previously mentioned, make sure the idle solenoid is functioning.

 

mike

[John76]

Couple of things to check....

Your video sounds like you have some vacuum leak problems.

There is a vacuum port on the lower front of the Solex DIDTA which connects to the "absent" fuel return valve. Is this open?

This is a weird type of ported vacuum source. It is open (pulls vacuum) at idle, and none when the throttle is cracked.

Where does that black vacuum hose (next to the idle air control screw) connect to? Stick your finger over the end to feel for vacuum, and plug if you do.

Looks like your idle cut-off solenoid is new. Double check that all three electrical connections to the Solex are energized with +12 V when the ignition is on. These are the solenoid cut-off, electric choke, and the air-temp switch (between #3 & #4 intake runners). These are all fed with a green/white wire located inside the blue sheathing.

Do you have the Solex instruction sheet? There are many small steps that must be carefully executed to make everything work. Remember, '75 -'76 was the height of the anti-smog years for the last of the carbureted '02s.

 

[7sis]

Thanks so much for the great info, I'll try spending a bit more time on the car over the weekend..

 

@mike From what I see, might be surprising but fast idle cam mechanism seems fine! Works pretty smoothly, I don't suspect this to be the problem.

 

@John76 @'76mintgrün'02yes I've replaced the idle solenoid valve 4 years ago and don't suspect it to have failed, else they would be highly unreliable!! (Did about 500miles since and car is parked in a heated garage!) . Still I'll try to listen to it with 12v on to ensure it still works!

 

@John76 Vacum could be the most probable root cause from the sound of the engine as you state...  I'll be looking at the the black vaccum lines as you suggest...  I believe I forgot to reconnect the carb to the fuel return valve which is currently loose and sort of hanging...

 

For the idle mixture, idle air control and idle speed screws what would be a good starting point? I got from another post an old guidebook for the solex 2bbl:

-idle mixture: turn in until bottomed then unscrew 2 2/3

-idle air control: turn in until bottomed then unscrew 5/3

- idle speed screws: ?

which seemed a bit different than mine from the pictures (were there different versions?)

 

I'll keep you posted with my further investigation results...

 

 

[John76]

5 hours ago, 7sis said:

idle speed screws: ?

The idle speed screw came with a USA mandated security cap. It was set at the factory and was not supposed to be tampered with.

However.....I'm one who is always curious, and wants to try to improve whatever the factory deemed "good enough".

Yes, there were two Solex 2-barrel carb versions. The TDID and the DIDTA, the USA model (with vacuum controlled secondary, water and electric choke, and provisions for a dash pot).

Slightly different initial set-up numbers for the DIDTA:

- Idle mixture 2 1/2 turns out

- Idle air screw 5/8 turns out

- Idle speed screw....no published value since we are not suppose to mess with it.  When the carb is off, you can see where the primary butterfly is cracked open at idle just enough to cover one of the tiny transition holes.

[7sis]

So finally had time to play a bit with the car yesterday...

1- Reconnected the front vaccum lines to the fuel return valve

2 - validated that idle solenoid valve "clicks" when it gets 12v...

3 - Adjusted idle mixture and air screws as suggested above

 

Result: car started cold then started revving at 2500 rpm for about 1min without me depressing the gas pedal, then rpm slowly reduced to 1200rpm then engine died... To keep the engine alive I have to "kick" the gas pedal very quickly when I see RPM is getting lower...

 

Any other ideas what could be wrong?

Could this behavior be symptomatic of Carb floats/needle valve not being properly set up? This is where my poor diagnostic skills would point me to... I thought I had put them to spec but might have to reopen the carb to verify...

 

Thanks again!

 

 

[7sis]

So, per my last post, thought this could be float/needle valve related, so opened the carb up today and checked the float, needle valve assembly etc and everything seemed fine. Re-installed everything and same behavior as before... 

 

Now what should I check next?

1 - Check all vaccum lines (easier)

If everything is ok with #1 should I go with the following which is way more involving (I've never done it before but this might be the time to do it....)

2 - Check valve clearance

3 - Adjust points (or replace)

4 - Re-do timing

 

Thanks

Edited April 23, 2020 by 7sis