How do you adjust an IDF accelerator pump?

[grungeant]

On a Weber IDF 40, do you tighten or loosen the nut on the accelerator pump rod to squirt a little more gas?

It looks like if I loosen the nut it would move further when the throttle is opened.
I just wanted to make sure before I did anything. Does loosen mean more squirt?
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1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

before you adjust the accelerator pump make sure that the mixture and timing advance are both correct and working properly.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grungeant]

All that is done.
Am I correct in thinking that backing the nut off will give me a little more squirt?
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

I am looking. Are you dealing with a flat spot? Black smoke or pop? Do you have an aftermarket cam or original?

This is from 914world

[grungeant]

I've been running the carbs the way they are for almost 2 years.
The engine is an 1800. And I think the carbs are about 3-4 years old.
I don't remember what my bigger jets are, but I sent many emails back and forth with the guy from aircooled.net to figure out what size everything was and what I should have. I think the throats are 34mm? But I can't remember for sure. whatever they are is what he said they should be. Same with my high rpm jets and emulsion tubes, and I can't remember what they are at all. My air corrections are 175. My idle jets are .50. I've tried everything in increments of .01 up to .54 idles and anything bigger than .50, even .51 made it smell too rich.
I have a pertronix 009 with pertronix coil. I'm at 32° advance at 3000. My dwell is 54.
By the way I am right at sea level, or just a few feet above.

Where it is now it idles good and strong at 900 and does not bother my eyes or sinuses.
When I put the snail meter on, it read 7 on cylinders 2 and 4. And 6 on cylinders 1 and 3.
I have not touched the air bypass screws at the base of the carburetors. Should I play with them to get all four throat's reading the same?

I need to wind my gears out pretty high and when I get back on it I need to kind of play with the throttle a little to keep it from popping and stumbling slightly and stay smooth. This usualy means going to about half throttle when I get back on and kind of feathering it back and forth between 1/4 and 1/2 as it slowly accelerates to a certain point, then I can jump on it and it will stumble very slightly and go.
It seems like if I accelerate very fast and rev very high and get back on it very hard and fast after a shift it goes better. But I don't like to feel like I have to beat the balls off it all the time.
There is no smoke.
I have been driving it this way for so long, I don't even really think about it. I just drive it.

I read something on a 914 forum where someone described my exact symptom of playing with the throttle to keep it from popping or stumbling at lower rpms and the solution was to increase the accelerator pump squirt 1/4 at a time till the stumble is gone.

I don't think the nuts are all the way in, but they are in pretty far.
When I first got the carbs a guy that knows carbs took them apart and cleaned them and adjusted the floats and accelerator pumps.

I'll check out your link when I have more time.
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

with the engine at idle you can cup your hands around the top of the IDfs. If the RPM drops they are too rich, if it rises it is too lean. You are just making it a little harder for the air to come in, not completely choking it. You can do the same at 2000 RPM and get a general feel for the mixture. Personally I would use an air to fuel meter to get the mixture right. As to sync, I like the carbs to have the same draw as close as possible both at idle then again about 1600 RPM. Once the mixture is dead on then adjust the accelerator pump for the smoothest acceleration.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grungeant]

The carbs are drawing the same air. At idle the front throats are both drawing 6 and both back throats are drawing 7.
Is there a way to adjust so both front and rear draw the same amount?
Is that what the air bypass screws at the base of the carbs are for?
Everyone I ask says don't mess with those screws, so I haven't. They also say that 6 and 7 is very close, and both carbs match, so leave it alone.
I've also been told because both throttle plates are attached, and on the same shaft, there's no way to adjust them individually to make them draw the same, which makes sense to me.
Unless there is something I can do with the screws at the base of the carbs.

I do not have an a/f meter, and I don't know anyone with one. For years I've been slowly turning the mixture screws in till they start to pop a little then slowly backing them out till they run good again. I would go around 2 or 3 times, and that has worked pretty well.

This time I actually used my tach and watched to where I actually get the highest rpm from each, and then when I go too far out it drops about 25rpm, so I go back in. This seems to have gotten me very close to perfect.
I'm pretty sure I'm about as close as I can be with the equipment that I have.

I think now I need to go 1/4 to 1/2 turn more squirt on my accelerator pumps.

I just read the link you sent me. I have read it before. Based on that it seems like I am correct in thinking I need more squirt. I'm guessing when the guy cleaned my carbs and set the floats and accelerator pumps, he set them to the base squirt setting. I have no way to capture the squirt or measure it. Just an assumption that the guy did it correctly.

Can you tell me which way to go?
Tighten or loosen the nut?
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

articles online state that making the rod shorter (nut in) increases the volume by pulling the diaphragm towards the lever. There are also a lot of articles on how to choose the proper venturi size to stop what you describe. And an article where people have not properly aligned things putting the IDF's back together so that the real problem is the accelerator pump passage is blocked.

When you set your timing see where the advance starts to come in. If it is late coming in, which some Industrial distibutors are, that can cause a stumble. I ran a German Bosch 009 for about a year but went back to a vacuum advance with cent advance distributor because it gave better mileage. Industrial engines are often like aircraft engines - they are designed to operate in a very narrow stable RPM range whereas car engines operate in a wide range. For that reason a SVDA is a better choice in distributors if there is a ported vacuum outlet on one of the carbs.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grungeant]

The guy from aircooled.net described some mathmatic equation based on my valve sizes and engine displacement or something?
I didn't really care how he concluded it, but he did determine my venturi size was correct for my application.

My distributor is a 009 made by Pertronix. The previous owner told me it was installed in 1998. The distributor says Pertronix on it, and the hole on the side is plugged with some sort of factory metal cap.
I'm guessing by the age, it's probably a first generation Pertronix.

I kind of doubt that the accelerator pump passage is blocked. I bought these carbs new, and it has always done it. Things I've done like changing jets or making adjustments made it slightly better, but never got rid of it.
I never messed with the air bypass screws or the accelerator pumps.
That's why I think it might be time to try the accelerator pump.
I will try a 1/4 tighter on each accelerator pump rod. Most of the stuff I read about adjustment is for the older style with a cam lobe or something. I don't really know.

What's weird is that it seems like the diaphragm is partially pushed as it is. Unless there is alot of freeplay in that lever before it actualy moves the diaphragm inside. It looks like the actual lever is pushed about 3/4 of it's travel, and when I open the throttle it only moves the last 1/4 of it's throw.
Unless I am not understanding what is going on inside correctly?

I read a few things that say there's only about 1/8-1/4" of threads exposed when the rod is correct. From the best of my memory, without looking at it, I think I have about 3/4" of threads exposed.
That's why I though if I backed the nut off, it would increase the throw or travel of the diaphragm, and therefore squirt more fuel when it moves.
But like I said. I may not be understanding what is actually going on inside the diaphragm housing.
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

7mm is what I saw earlier. That is slightly under 1/2 inch. Good luck.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grungeant]

A few weeks ago I turned both accelerator pumps up 1 full turn. It got a little better. So I turned them up another full turn. I drove it that way for a while, and it was better, but still not what I would consider "good" sometimes it was better than others. Sometimes it would pop, but it wasn't always the same cylinder, or even the same side, and simetimes I would smell gas, but I never saw smoke.

2 days ago I was thinking maybe they weren't even? So I turned both all the way in and counted the turns.
The left side was backed out 2 turns and the right was only backed out 1 turn. So I set them both to 2 turns out, and it was alot better. I turned them both in another 1/4 turn, and it got even better.
My throttle response is so crisp, and my bus accelerates better than it ever has. It is way smoother at low rpms driving through town. I get so much throttle response between closed throttle and about 1/4 throttle. The are both backed out about 1.75 turns from all the way in.

It's still not 100% perfect. I checked for vacuum leaks today, but didn't find any. When I get some more time I am going to take my idle jets out and clean them, and clean whatever I can see from the top without taking the carb apart.

If I go steady speed of about 25mph in 2nd gear, which is near the top of the comfortable steady spead for 2nd, and try to give just a hair more throttle I get some pops.
Would that mean my high rpm jets are too lean?
If I open the throttle a lot at 25mph it accelerates better.
I don't have a tach, but I am running 195R14, and I have a 6rib trans.
Any guess what rpm that might be?

My idle jets are .50 and my air jets are 175. I don't remember what my high rpm jets were or my emulsion tubes were, but they were what the guy from aircooled.net recommended for my setup at sea level. And I don't know what my accelerator pump jet is. This is the first time I ever touched the accelerator pumps on these carbs.
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[SGKent]

go up one main size on both carbs. Too bad you can't put an air to fuel gauge on it and just dial it in.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grungeant]

Is the "main jet" the high rpm ones, or the idle jets?
When I use anything bigger than .50, even .51 it idles too rich.
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[Lil Lulu]

Well grungeant, as you can see, you will not likely get a straight answer to the question “nuts in more squirt or nuts out more squirt?”
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'65 Beetle "Lil' Lulu"- Ruby Red
1600 stock from '71 bus

'72 Deluxe - Niagara Blue w/pastelwiess Camper Special 2L dual 40 Webers 002

'74 Hightop Weekender "Dixie" 1800 34 Del singles

[grungeant]

I just found this old picture.
Looks like my emulsion tubes are F11, and my high rpm jets are 115.

So do I need to order 120 jets to go up a size?

_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig

[grungeant]

[grungeant]

Is the accelerator pump supposed to squirt the full travel of the throttle plates?
I noticed I am only getting squirt for about 3/4 throttle. The last quarter throttle there is no squirt.
What does that mean?
Does this mean I adjusted my accelerator pump too tight and it's dumping all it has too soon?
Does this mean I need bigger accelerator pump jets?

I am waiting on parts right now.
I ordered jet doctors for the idle jets, and 1/2" phenolic spacers. I also ordered the 120 mains and the longer emulsion tube holders. I had the short emulsion tube holders that stay below the air cleaner plate, and they always got specs of stuff in the tops.
Once I take the tops off to install the jet doctors, I am going to clean everything out and check my float settings too.

Is there anything else I should take notice of or measure and mark down while I'm inside?
_________________
1974 Tintop with a nice rack

"You should remember it's peace of mind you're after, and not just a fixed machine."
Robert Pirsig