Carb questions

[Chazwars]

1972, VIN BS1

I can't seem to pinpoint specific solutions in searches for the following:

I've noticed that one of my barrels on a single dual barrel carb is always dry. Additionally, I am getting horrid mpg (12c/17h). Lastly, I'm getting the black discharge from the exhaust- even after a warm start. I'm working through artigue's manual (amazing) yet I'm struggling to identify different parts.

Questions:
-Is there an issue if one of the barrels in completely dry? (I'm testing it with the throttle pulled out and no choke)

-Is there a way to adjust the floats? I'm noticing some leakage on the top of the float container. (sorry, at work and procrastinating, so I can send pics later if needed).

-How about figuring out appropriate mixture to determine richness? I'm struggling to get a feel for proper mixture.

[seabeelt]

First, DMSA?? 1,2 or 3. I just took one off of our 71 and was getting in the mid 20's for mpg average - Just switched to dual 40 IDFs

You may need a carb rebuild kit. Sound like the needle seat is not closing all the way, and or your float is bad ( possible but not likely) If I remember correctly, only one of the barrels has the little holes in the barrel side wall. Also could be running very rich. What do the plugs look like?

[Dougieb]

I believe a '72 should have a DHSA originally.
I could never get mine to dial in acceptably.
I went to a DMSA with a single plane manifold and have been happy ever since.
But that is just my opinion.

[Chazwars]

I'm going to assume it is a DHSA 2.

Thanks for the feedback. I should probably do the rebuild anyways. I have no idea when it was done last. I've learned that it is just better to replace rather than assume it will work for a while. I was just hoping to avoid engine work until next winter. hahaha. Rookie mistake.

[seabeelt]

My Bad, DHSA. No rookie mistakes here. My MC went last fall and I'm just now getting around to working on it. I still must have air in the system and the darned acorn nut is probably not adjusted properly as I have really really soft brakes that I have to pump to get to work. Maybe next weekend or the one after that

[Chazwars]

No worries. I'll try to get it all adjusted back to factory specs and see where I am at from there. Then, on to a rebuild if needed. I'll send some pics tonight if I run into any issues.

[DanD]

If you have the original carb, you have a vacuum operated secondary. If the diaphragm is shot, you have no second barrel. Others have pointed out that your fuel bowl is likely flooding.

[Chazwars]

Thanks Dan. That might be the ticket. I will say, I am having a heck of a time getting this thing dialed in. Based on a antigues specs, I am to adjust the idle screw to 900 then adjust mixture screw accordingly. But I am not understanding this idle jet. If I tweak the idle jet, it throws the rest of. I've had the mixture screw seated all the way in at throttle and still idling. It's confusing with the measurements of the idle jet. How am I to measure it to 45-55 etc (or whatever numbers acurately).

[majicwrench]

I'm confused (happens a lot) why are you messing with idle jet??

Does idle mix screw not affect idle quality?? It should be very poor w screw all the way in.

[Chazwars]

So, I've been trying to get this DHSA back to specs but when I get the idle screw set to run at 900 and the mix screw pulled out 1.5 turns, the exhaust is still sputtering and engine shaking. I've tried slight turns of the mix screw with no success. When it is fully seated, it stalls out completely. I've slightly lowered the float and no longer have the overflow from the carb. Now, when I pull out the idler jet very very very slightly, it seems to even everything out and she runs somewhat smooth. There is still fuel dropping in from the top. The problem is that if the carb shifts in any way, the idler jet gets misplaced again and the car runs bad again. I've also tried stopping the flow of fuel and just using fuel in the bowl manually (testing the psi). This seems to work ever so slightly only when the jets are tweaked slightly. I'm really struggling with this and just can't seem to get back to baseline. Sadly. I am looking back and seeing that maybe the mpg was just fine compared to where I am now. She barely stays idle at stop lights and sputters at about 3000-3600 in any gear. And the plugs are getting chared black!

[majicwrench]

Main issue for me is your terminology ( and my spelling). What the heck is "pull out the idler jet very very slightly"??

"Carb shifts (?) idler jet gets misplaced (?)" not sure what you mean.

Fuel should not drop in from top. This is usually cause you have throttle plate too far open.

[Chazwars]

I turn the idler jet on the main chamber counterclockwise slightly.
Carb shifts= vibrating ornwhen the engine is shaking, causes the jet to become more disengaged.
Interesting aboit fuel dropping from the top. I will look into throttle plate..
Thanks!

[majicwrench]

The idle jet is a small jet located behind a jet carrier that screws into the carb body and cannot be adjusted.
Do you mean the idle mixture screw??

[Chazwars]

The gold screw in the center of the pic is what I slightly turn out which affects fuel dropping into the carb from the top. The mixture screw is the silver on the bottom with the nut, right? Then the idler screw (where my screwdriver is situated) is to the right of the mixture screw right behind the throttle cable, right?

[Chazwars]

Well, I might have gotten somewhere.

1. I found the specs on the float to cover height and adjusted it to .25".

2. I then rotated the idle jet counterclockwise until no fuel released from the top of the barrel.

3. I double checked the fuel release when the throttle was engaged and the fuel being released was in a different outlet (more closer to the sidewall rather than the dead center like when the idle jet was seated).

4. I reset the mixture screw to 1.5 counterclockwise turns from seated.

5. Adjusted the slow idle screw to 900 rpm. I, then, went through the steps of bringing the carb back to specs.

Everything worked out accordingly. I did need to do some slight tweaking of the secondary barrel idle jet because it wasn't smoothly settling into gear while the engine was running at 3600-4200 rpm and opened up the mixture screw about a 1/4" more to reduce the backfire when downshifting. I haven't tested these last two minor adjustments so I'll report on the effects of these tweaks.

I'm still curious why adjusting the idle jet made all the difference.