Carter AVS Setup & tuning book/guide?

Sir Dodge alot

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Hey there gents, would appreciate some help or finger pointers on this matter.

Recently I was able to do a 2 to a 4 barrel conversion on a 361 motor.
(Stromberg WWC to a Carter AVS)

Problem now is I have no idea where and what to start adjusting to get the Carter AVS running right.

Feels like I'm in the dark adjusting screws and what not like as if I'm blind folded.

Is there some kind of book or guide I can purchase on adjusting & setting up Carter AVS's?

Or is a service manual the better choice?

Additional information: Carburetor came off of a 1968 plymouth roadrunner.

Thanks.
 
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On the Edelbrock website, they used to have a downloadable guide for tuning their/Carter AFBs. About 50 pages or so, downloaded and printed. Other than the normal idle mixture settings and such, it had procedures to do "on the road" tuning of the metering rods and such.

BUT as your carb is from a '68 383 RR, it should be almost exactly correct in the metering rod/spring areas. So no significant need to do anything other than set the idle speed (in the 650rpm range, in "P") for the OEM factory specs) and set the idle mixture at that speed by "lean best idle" method. Initially, at first, play like it's the '68 383 RR engine that it came off of. Then tweak from there.

Which cam is in your motor? As that can affect how the idle speed and mixture settings evolve.

Having a quality dwell/tach makes life easier and more precise. When I was trying to set idle mixtures via a vacuum gauge, things never did come out as I wanted them too. But in prior times when that vac gauge was a "high tech" tool and dwell/tachs were only in the larger garages, it probably worked well enough for the times. When I saved up and got a quality dwell/tach, I got much more precise results that I knew were right. FWIW

Glad your project is progressing!
CBODY67
 
On the Edelbrock website, they used to have a downloadable guide for tuning their/Carter AFBs. About 50 pages or so, downloaded and printed. Other than the normal idle mixture settings and such, it had procedures to do "on the road" tuning of the metering rods and such.

BUT as your carb is from a '68 383 RR, it should be almost exactly correct in the metering rod/spring areas. So no significant need to do anything other than set the idle speed (in the 650rpm range, in "P") for the OEM factory specs) and set the idle mixture at that speed by "lean best idle" method. Initially, at first, play like it's the '68 383 RR engine that it came off of. Then tweak from there.

Which cam is in your motor? As that can affect how the idle speed and mixture settings evolve.

Having a quality dwell/tach makes life easier and more precise. When I was trying to set idle mixtures via a vacuum gauge, things never did come out as I wanted them too. But in prior times when that vac gauge was a "high tech" tool and dwell/tachs were only in the larger garages, it probably worked well enough for the times. When I saved up and got a quality dwell/tach, I got much more precise results that I knew were right. FWIW

Glad your project is progressing!
CBODY67

When the 2 barrel was on the car I used to STRICTLY tune the A/F mix by looking at the plug color, then adjust the screws from there, just as you say the vacuum gauge would not bring me satisfactory results/adjustments so I'm a firm believer in plug reading tuning.

But no joke, vacuum gauges back then was like having an OBD scan tool equivalent.

Uncle tony discusses on the vacuum gauge also.

On how I tune the A/F mix:

I would go out of town in a secluded long road then WOT till 3rd gear @80MPH.

I turn the engine off and coast to the side of the road and remove the plugs.
Light Tan/brownish is the color I strive to get on the plug porcelain part.

And adjust the mixture screws from there.

Tools:

I have an electronic Innova timing light equipped with dwell/tach.

Plain old vacuum gauge.

My ears and nose.

Parts/mods on the car:

Mostly unknown, if it's straight from the factory, the motor has a forged Crankshaft, cast pistons, 2 barrel cam.
(I've heard there are different cams for a 2 barrel car and a 4 barrel car)

I likely have a 2 barrel hydraulic flat tappet cam, unknown lift/duration.

CVF RACING aluminum water pump housing.

Some of Mr. Gasket's recurve springs.

I did indeed see there is an Edelbrock tuning guide if you purchased an AVS 2 OR a Thunder series carbs.
But wasn't sure if most if not all of the information would apply to a AVS pre 1970's. (Different fast idle linkages and such)

Yes! It's quite exciting learning more and more on these old barges, me being a fairly young guy I have alot more room to grow!
 
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Thanks for the information. The reason I mentioned "cam" is that it can affect the needed air flow at hot base idle, which can relate to how far open the throttle plates are at that time. Usually, the "2bbl cam" from the middle 1960s was the 252/252/.390" cam, whose timing specs debuted on the 1958 350 2x4bbl Sport Fury engine. Those cam specs were used up through the 1966 model year on 383 2bbls. In '67, the 383 2bbl used the "Standard Cam" 256/260/.425" 4bbl cam (which debuted with the 440/350 in 1966). The '68 383RR cam would be 268/284, which debuted with the 1967 440/375 GTX. So, in looking at the '68 FSM, the hot base idle speed in "N" (per FSM) with the parking brake firmly applied, the idle speed is 650rpm, whereas the hot base idle with the 252 cam and 2bbl would be closer to or a bit below 600rpm in "N".

As for the idle mixture settings/adjustments, the carb specs list the idle speed screw "Turns Open" to be "1-2". So start with 1.5 turns open to get things going and the idle speed set. Then, adjust ONE screw inward about 1/4 turn and see how the speed might change. Leave it there, then do the same with the other screw. This is leaner in orientation and has NO bearing on how the plugs will color at WOT, per your testing technique.

In the "Lean Best Idle" method, you are looking to lean the mixture until you get to a point (from max rpm at idle) where that "leaner" adjustment resutls in a 20 rpm drop per screw. When that 20 rpm drop, happens, then richen just enough to regain the prior best rpm.

NOW, here's my shadetree method of idle mixture and speed, which I perfected in the earlier 1970s when there was still a bit of lead in the fuel and alcohol-based components were minimized.

With the engine fully warmed up and idling comfortably in "P" after the 20 rpm drops had been noted and compensated for. Nail the parking brake and carefully put the trans in "D", as it would be at a red light. THEN I'd quickly go to the end of the exhaust pipe and check for exhaust gas flow smoothness. I would set the speed just to where the pulses became a smooth flow, by feeling that with the palm of my hand. Or at least verify that the flow was smoooth at the prior rpm setting. Being in the exhaust gas flow, I would then smell my hand to check for "hydrocarbon" smell (indicating a bit too rich). Then I'd go back to the carb and lean the mixture 1/8 turn inward, recheck the idle speed gas flow, and then use my other palm to collect the hydrocarbon smell. After each mixture adjustment, you'd need to wait about 30 seconds to do another smell-check AND wash my hands between checks, too. This method seems to work much better on a single exhaust car, but can also work with duals, too.

With the idle mixture and in-gear speed set, then put the trans in "P" and re-check the idle speed. Also turn off the engine and see if it dies immediately. If it does not, then turn the idle speed screw to about 1/4 turn slower. Re-start the engine and cycle repeat for the idle mixture and gas flow smoothness. A "cut and try" process, but when done, everything should be as good as you can get it, regarding idle speed, going into gear nicely with no harsh engagement, smooth and reliable idle speed, and no dieseling when turning off the ignition.

When I was prototyping this procedure, I might initially consume at least 30 minutes to get it done. Not sure if the smell check will work with unleaded fuels or ethanol variations of it. In some respects, it can be a bit of over-kill past the Lean Best Idle method of adjustment, but using the rpm when the idle pluses become a snooooth flow (in gear) can still be used, I suspect. In the mean time, that "20 rpm drop" aspect of things can work well by itself. In any event, the ultimate goal is to have the engine idle as lean as it can and still be smooooth at a particular hot base idle rpm. WITHOUT needing an air/fuel ratio meter to do it. Which is what the 1968 FSM says to use, per the new-for-back then underhood Emissions Decal was for (hot base idle speed at a stated air/fuel ratio from the meter).

Back then, too, I had plenty of time and motivation to spend time doing these things. Things have changed a bit since then. So proceed as you might desire.

BEFORE undertaking these things, verify the ignition point dwell (if equipped with ignition points) and then the hot base ignition timing (vac advance unhooked and plugged), in that order.

Have FUN!
CBODY67
 
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Thanks for the information. The reason I mentioned "cam" is that it can affecgt the needed air flow at hot base idle, which can relate to how far open the throttle plates are at that time. Usually, the "2bbl cam" from the middle 1960s was the 252/252/.390" cam, whose timing specs debuted on the 1958 350 2x4bbl Sport Fury engine. It was used up through the 1966 model year on 383 2bbls. In '67, the 383 2bbl used the "Standard Cam" 256/260/.425" 4bbl cam (which debuted with the 440/350 in 1966. The '68 383RR cam would be 268/284, which debuted with the 1967 440/375 GTX. So, in looking at the '68 FSM, the hot base idle speed in "N" (per FSM) with the parking brake firmly applied, the idle speed is 650rpm.

As for the idle mixture settings/adjustments, the carb specs list the idle speed screw "Turn Open" to be "1-2". So start with 1.5 turns open to get things going and the idle speed set. Then, adjust ONE screw inward about 1/4 turn and see how the speed might change. Leave it there, then do the same with the other screw. This is leaner in orientation and has NO bearing on how the plugs will color at WOT, per your testing technique.

In the "Lean Best Idle" method, you are looking to lean the mixture until you get to a point (from max rpm at idle) where that "leaner" adjustment resutls in a 20 rpm drop per screw. When that 20 rpm drop, happens, then richen just enough to regain the prior best rpm.

NOW, here's my shadetree method of idle mixture and speed, which I perfected in the earlier 1970s when there was still a bit of lead in the fuel and alcohol-based components were minimized.

With the engine fully warmed up and idling comfortably in "P" after the 20 rpm drops had been noted and compensated for. Nail the parking brake and carefully put the trans in "D", as it would be at a red light. THEN i'd quickly go to the end of the exhaust pipe and check for exhaust gas flow smoothness. I would set the speed just to where the pulses became a smooth flow, by feeling that with the palm of my hand. Being in the exhaust gas flow, I would then smell my hand to check for "hydrocarbon" smell (indicating a bit too rich). Then I'd go back to the carb and lean the mixture 1/8 turn inward, recheck the idle speed gas flow, and then use my other palm to collect the hydrocarbon smell. After each mixture adjustment, you'd need to wait about 30 seconds to do another smell-check AND wash my hands between checks, too. This method seems to work much better on a single exhaust car, but can also work with duals, too.

With the idle mixture and in-gear speed set, then put the trans in "P" and re-check the idle speed. Also turn off the engine and see if it dies immediately. If it does not, then turn the idle speed screw to about 1/4 turn slower. Re-start the engine and cycle repeat for the idle mixture and gas flow smoothness. A "cut and try" process, but when done, everything should be as good as you can get it, regarding idle speed, going into gear nicely with no harsh engagement, smooth and reliable idle speed, and no dieseling when turning off the ignition.

When I was prototyping this procedure, I might consume at least 30 minutes to get it done. Not sure if the smell check will work with unleaded fuels or ethanol variations of it. In some respects, it can be a bit of over-kill past the Lean Best Idle method of adjustment, but using the rpm when the idle pluses become a snooooth flow can still be used, I suspect. In the mean time, that "20 rpm drop" aspect of things can work well by itself. In any event, the ultimate goal is to have the engine idle as lean as it can and still be smooooth at a particular hot base idle rpm. WITHOUT needing an air/fuel ratio meter to do it. Which is what the 1968 FSM says to use, per the new-for-back then underhood Emissions Decal was for (hot base idle speed at a stated air/fuel ratio from the meter).

Back then, too, I had plenty of time and motivation to spend time doing these things. Things have changed a bit since then. So proceed as you might desire.

BEFORE undertaking these things, verify the ignition point dwell (if equipped with ignition points) and then the hot base ignition timing (vac advance unhooked and plugged), in that order.

Have FUN!
CBODY67

I Set the point gap at 30 with the dwell meter, vac can is plugged off at carb base.

"
When I was prototyping this procedure, I might consume at least 30 minutes to get it done. Not sure if the smell check will work with unleaded fuels or ethanol variations of it."

Funny you mention that, few months back i recall smelling my hand near the exhaust while the motor was running, the exhaust flow seemed more of a puff puff puff everytime a cylinder fired, and hand was ever so slightly wet, too rich?

"
With the engine fully warmed up and idling comfortably in "P" after the 20 rpm drops had been noted and compensated for. Nail the parking brake and carefully put the trans in "D", as it would be at a red light. THEN i'd quickly go to the end of the exhaust pipe and check for exhaust gas flow smoothness. I would set the speed just to where the pulses became a smooth flow, by feeling that with the palm of my hand. Being in the exhaust gas flow, I would then smell my hand to check for "hydrocarbon" smell (indicating a bit too rich). Then I'd go back to the carb and lean the mixture 1/8 turn inward, recheck the idle speed gas flow, and then use my other palm to collect the hydrocarbon smell. After each mixture adjustment, you'd need to wait about 30 seconds to do another smell-check AND wash my hands between checks, too. This method seems to work much better on a single exhaust car, but can also work with duals, too."

So if i'm reading this correctly, you adjust the idle speed only when your mixture screws are set? and not "Cheat" the RPM adjust with the curb idle screw.

"
Usually, the "2bbl cam" from the middle 1960s was the 252/252/.390" cam, whose timing specs debuted on the 1958 350 2x4bbl Sport Fury engine. It was used up through the 1966 model year on 383 2bbls. In '67, the 383 2bbl used the "Standard Cam" 256/260/.425" 4bbl cam (which debuted with the 440/350 in 1966. The '68 383RR cam would be 268/284, which debuted with the 1967 440/375 GTX. So, in looking at the '68 FSM, the hot base idle speed in "N" (per FSM) with the parking brake firmly applied, the idle speed is 650rpm."

One thing that makes me think now is that the motor has serious asthma with the tiny cam and the 516 heads with the 1.60 EXH valves.
Great.

Sorry about the half assed responses i gave, I'll reference this information again, still processing all the info you have written down, much thanks.

The carb "adjustments" I made are in no way reliable, i think the choke is out of whack so the motor gargles on fuel within the first 5 seconds of starting and wants to stall.
I'll reference this information and refer to the service manual @Big_John has graciously provided me.
 
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That "tiny cam" and 1.60" exhaust valves build mid-range torque that works well with the 2.76 rear axle ratio . . . on the road. In so many cases, from my orientation, building "a torque motor that rpms" can make a nice-performing vehicle. Especially with the tighter torque converters Chrysler tended to use back then.

NOT to forget really good highway fuel economy, especially at 55mph. The first trip home I made with the 55mph national speed limit, in the '66 Newport 383 2bbl (with a Holley 2210 rather than the OEM Stromberg WWC3 2bbl) recorded 20mpg at that lower, steady speed. Whereas on an up to 90mph cruise in deepest, darkest West TX on I-20 one night, averaged 15mpg, with the OEM Stromberg when the car was about 2 yrs old.

That car had a natural cruising speed range of 75-90mph, which was neat. At 70mph and below, it was "bored", but nudge just to 75mph and it was "This is FUN, lets do more". But past 90mph, the factory suspension (even with later HD shocks), was a bit busy in nature, as in "not fun up here". 90mph is fast enough, anyway. All of the vehicular dynamics were all working together for a nice ride and engine performance in that 75-90mph speed range, on that car. AND all of that happened at about 3400rpm or less.

As for the idle setting procedure, you have to start with the idle speed screws at 1.5 turns out to get the initial hot base idle speed setting. Then play with the mixture screws and see how things go from there. If the idle speed (after getting it maxed) needs to come down (after it might increase to more than 650rpm), decrease it and continue to fine tune the mixture until the 20 rpm drop is achieved with the ending idle speed still being 650rpm.

OR, you can start with the idle mixture screws at 1 turn out, set the hot base idle rpm to 650rpm, and turn each mixture screw out about 1/8 turn at a time until max rpm is reached, then decrease the idle rpm to 650rpm and re-tweak the idle mixture screws until that 20 rom drop happens on each mixture screw.

Enjoy!
CBODY67

CBODY67
 
That "tiny cam" and 1.60" exhaust valves build mid-range torque that works well with the 2.76 rear axle ratio . . . on the road. In so many cases, from my orientation, building "a torque motor that rpms" can make a nice-performing vehicle. Especially with the tighter torque converters Chrysler tended to use back then.

NOT to forget really good highway fuel economy, especially at 55mph. The first trip home I made with the 55mph national speed limit, in the '66 Newport 383 2bbl (with a Holley 2210 rather than the OEM Stromberg WWC3 2bbl) recorded 20mpg at that lower, steady speed. Whereas on an up to 90mph cruise in deepest, darkest West TX on I-20 one night, averaged 15mpg, with the OEM Stromberg when the car was about 2 yrs old.

That car had a natural cruising speed range of 75-90mph, which was neat. At 70mph and below, it was "bored", but nudge just to 75mph and it was "This is FUN, lets do more". But past 90mph, the factory suspension (even with later HD shocks), was a bit busy in nature, as in "not fun up here". 90mph is fast enough, anyway. All of the vehicular dynamics were all working together for a nice ride and engine performance in that 75-90mph speed range, on that car. AND all of that happened at about 3400rpm or less.

As for the idle setting procedure, you have to start with the idle speed screws at 1.5 turns out to get the initial hot base idle speed setting. Then play with the mixture screws and see how things go from there. If the idle speed (after getting it maxed) needs to come down (after it might increase to more than 650rpm), decrease it and continue to fine tune the mixture until the 20 rpm drop is achieved with the ending idle speed still being 650rpm.

OR, you can start with the idle mixture screws at 1 turn out, set the hot base idle rpm to 650rpm, and turn each mixture screw out about 1/8 turn at a time until max rpm is reached, then decrease the idle rpm to 650rpm and re-tweak the idle mixture screws until that 20 rom drop happens on each mixture screw.

Enjoy!
CBODY67

CBODY67
YES i have also achieved 18+- MPG on frontage roads @40/50 MPH from San Antonio TX to Dallas Fort worth TX not bad MPG's for a big block!
I have the mixture screws set at 2 turns out of the seat, will adjust to 1 turn out from the seat tomorrow.

Question: "start with the idle speed screws at 1.5 turns out"

Is that out from the screw stop? or from the hole the screw screws IN to? sorry about the strange question. AND is the idle screw OFF of the fast idle cam while i set this?
This may click for me once i'm back to tinkering on the carb.
 
I have a question regarding the divorced choke adjustment, (Was not covered in the PDF, or i didn't see it...) i set the bimetalic spring to go FULL rich setting as the choke flap does not fully close. unless it's supposed to be like that, may have been the unadjusted fast idle cam link, maybe?

20220828_235207.jpg
 
Screw the idle mixture screws "in" with your fingers, to lightly seat them, THEN screw then outward to the initial setting.

Do NOT adjust the choke thermostat spring from the initial setting, which should coincide with the setting mentioned in the FSM's Specs page. At ambient 70 degrees F, the choke plate should just close by itself, with the choke pull-off openning it enough to keep the engine from choking down due to a too rich condition. "Ambient" meaning the air surrounding the carb and the engine/carb themselves at that same temperature. In our 90+ degree F days, it should not close all the way, so for now, just go with the factory setting and worry about the other setting when the weather gets cooler.

The rh speed screw is for the fast idle speed adjustment. The lh speed screw is for the hot base idle speed adjustment.
 
Screw the idle mixture screws "in" with your fingers, to lightly seat them, THEN screw then outward to the initial setting.

Do NOT adjust the choke thermostat spring from the initial setting, which should coincide with the setting mentioned in the FSM's Specs page. At ambient 70 degrees F, the choke plate should just close by itself, with the choke pull-off openning it enough to keep the engine from choking down due to a too rich condition. "Ambient" meaning the air surrounding the carb and the engine/carb themselves at that same temperature. In our 90+ degree F days, it should not close all the way, so for now, just go with the factory setting and worry about the other setting when the weather gets cooler.

The rh speed screw is for the fast idle speed adjustment. The lh speed screw is for the hot base idle speed adjustment.
"Screw the idle mixture screws "in" with your fingers, to lightly seat them, THEN screw then outward to the initial setting."

Oh Ok, idle speed screws are mixture screws? I believe i got that down now, Mixed up with the idle screw & the mixture screw,
(The screw that controls the RPM)

i'll adjust the idle speed screw to 1.5 out from seat.
Will reset the setting on the bimetallic spring on the divorced choke, I assumed the choke spring is set a tad lean due to it being NOS
Yes indeed it's going to get chilly in a few months or so, hopefully the motor will at least start reliably till then or else i'm working in the fridgid Texas winter weather!
Still have yet to get a replacement heater core also, time is ticking!
 
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NO! Although the mixture screws (rich or lean) can affect idle speed, but AFTER the idle speed screw (lh side of the carb, by the throttle linkage) has been adjusted to the hot base idle speed. There is no "turns out" spec for the idle speed screw.

On some 1968-era carbs, there is a larger screw above the idle mixture screws which can affect idle air supply. Consult the 1968 Plymouth or Dodge FSM to see about that screw being or not being on your carb. And how to deal with it.
 
NO! Although the mixture screws (rich or lean) can affect idle speed, but AFTER the idle speed screw (lh side of the carb, by the throttle linkage) has been adjusted to the hot base idle speed. There is no "turns out" spec for the idle speed screw.

On some 1968-era carbs, there is a larger screw above the idle mixture screws which can affect idle air supply. Consult the 1968 Plymouth or Dodge FSM to see about that screw being or not being on your carb. And how to deal with it.

Yes I believe, i have that "air bleed" screw according to the old 1968 master Tech slideshow video volume 68-2.


The only spec I got floating around on the internet is screw adjustment is 1 turn out from seat as an basic starting adjustment. With the air bleed screw.

I'll get a FSM if the one @Big_John provided me does not explain it.

But I reckon the air bleed screw can be tuned as normal,
(Just like the mixture screws) with the vacuum gauge.
(Achieving highest vacuum/highest idle)
Am I off base?

Below is the picture with the 3 adjustment screws.

20220817_143825.jpg


Aside from that, I will start off today with the mixture screw settings at 1.5 turns out, and reset the divorced choke coil tension back to factory spec.
(1 notch rich?)
 
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Reset the bimetalic coil on the divorced choke back to near stock settings.

Next: adjusted the mixture screws to 1.5 turns out of seat.
(Previously set at 2 turns out of seat, may have been a contributing factor on why the motor was gargling on fuel on startup, and the misadjusted divorced choke coil)

Stock NOS fast idle linkage was good enough, no bending of the linkage was needed, gap at the choke valve was close.
(About .068 instead of the .055 the instruction calls for.

Didn't have a .055 bit so I stacked a couple feeler gauges to get the similar setting when the choke valve is closed.

The feeler gauges I stacked to adjust the choke flap is listed below.
.035 (0.88MM)

.0015(0.04MM)

.002(0.05MM)

.0025(0.06MM)

.003(0.08MM)

.004(0.10MM)

.005(0.13MM)

you should feel a slight drag pulling the bit/feeler gauge out, according to the instruction sheet.

20220829_110331.jpg


20220829_120222.jpg


20220829_120600.jpg


20220829_123635.jpg
 
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The motor starts but stalls after 5 seconds, I'll peruse the FSM in the meantime.

Few nights ago, the cure to this issue was to ramp up the idle with the idle screw turned in yay high.
And take a chopstick on the choke flap rod and prevent the pull-off from opening the choke flap any further.

Still, sounds like a choke issue now.
Choke flap goes into a 45* angle once the engine starts. And there's too much air and not enough fuel.

I'll adjust and test and test and retest the pull-off rod linkage.
 
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Ok, I think I'm on to something.
Stretched/bent the choke pull-off rod so it stretches farther back toward the back of the carb.

Idled smoother longer but there still seems to ba a slight choke problem as the engine idles down still too soon.

There's a whistling noise coming from the carb now.
(Intake noise? Vacuum leak?)

Will adjust choke pull-off rod a bit more to see if I can get a stable idle.
(WITH NO CHOPSTICKS THIS TIME)
At this point, the car is going to become an oriental Chrysler lol.

And yes, the pull-off rod is incorrect for an AVS carb, the pull-off rod is from my AFB parts pile.

20220829_145949.jpg
 
Motor starts & "idles" on 1st key crank.
(Very good so far)
But here's the catch, the motor is idling at 1000+ RPM.

Mixture screws don't do anything, idle speed screw backed all the way off.
Still idles high.

Found a vacuum leak of biblical proportions on the back of the carb's insulator gasket.

Is sandwiching gaskets on the insulator good here?
I reckon that's the only thing I can do is that like this picture's setup.

Screenshot_20220829-165536_Chrome.jpg


20220829_164814.jpg


20220829_164157.jpg
 
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