Single Carb Getting Better But not There Yet, OVER IT! Went with Dual 44s Options

[Mblizzard]

Yea it is kind of a waste (Weber 36/38 DVG) but I have a number of projects that are sucking up $$$ so I am trying to make it a while with this set up. Had a huge stumble before changing to the 60s on the Accelerator jets. The stumble is mostly gone now. Waiting for a 70 to come in. But while its better, it seems to not want to idle. Regardless of how I try to adjust it acorroding to the instructions, it seems to want to die. At anything above idle it seems to be fine. The problem was there before the change but it was no better after. Did a good cleaning on everything else but did not change anything other than the accelerator diaphram. One thing I noticed is that fuel seems to be dripping into the primary. I am not sure if it was like this before as I had not looked in.

I am assuming this is not normal, so any thoughts on what I goofed up?

[rhodyguy]

the CB book doesn't list yours but does show a 32/36 DGAV. you cleaned the primary and secondary idle jets?

k

[Mblizzard]

I will have to check the number I went on memory. 32/36 DGV. I pulled everything out cleaned with carb cleaner spray and compressed air. I pulled the idle jets again and checked them again and they seemed clear.

[struckn]

Float struck Open? Fuel pressure?

[Mblizzard]

Had not thought of the float. I checked before reassembling it and it was free. I have a pressure regulator so I don't think it is the pressure. I did not notice any difference in the emulsion tube. The only thing I might have mixed up was the main jet. But it would not cause the continual stream if gas.

I was able to verify that the accelerator jets added additional fuel so I don't think it is leaking there.

[Mike Bellis]

Do you have this???

 Webber_28_36dcd_manual.pdf ( 2.06mb ) Number of downloads: 370

[Mblizzard]

No I don't have that. Thanks. More readin!

[vw505]

My Webpage

0) Set ignition dwell & timing first.

1) Idle Speed Screw: 1 turn open from *just* touching the tab

2) Idle Volume Screw (sometimes wrongly called the "Idle Mixture screw"): 2 turns out from LIGHTLY bottomed.

3) Start Engine

4) Adjust Idle Volume to highest idle speed while counting the turns or partial turns from the lightly bottomed position. Btwn 1-3/4 turns to 2-1/4 turns is where you want to be.
If more than 2-1/4 turns then Idle Jet is Lean - Increase jet size.
If less than 1-3/4 turns then Idle Jet is rich - Decrease Jet size.

5) Mains should start to drip out of the booster venturis at 3500 RPM
If the RPM is higher the Jets are too small. (See note on Air Corrector Jets)
If RPM is lower then the jets are too big. (See note on Air Corrector Jets)

Air Corrector Jets:
I do not have any simple way to tune these. They are modifiers of the range of the main jets & too a lesser degree the Idle jets. Air Jets have a progressively increasing (leaning) effect as the RPM's increase. And being that they are air jets, the larger they are the leaner the given mixture. It is possible to have two main jet & air jet combo's 'tip-in' at the same engine speed, and perform totally differently.
They can also be used, once your jetting is satisfactory, for altitude correction. There's a Rule Thumb that for every 2000 feet in altitude you can reduce the Air Corrector one size, but every engine will be a little different. Let experience by your guide here.

Emulsion Tubes:
They are located under the Air Corrector Jets. These are a black art. They are numbered in sequence of mfg, not progressively. An F4 preceeds an F5, but while an F4 might be nearly perfect for a 275 GT SWB Lusso V12 Ferrari, the F5 might have been developed for a 995cc Mini engine.
You will have to hope that the seller of your carb set it up with the correct Emulsion Tubes & leave them alone until you become an advanced Weber tuning guru.

Some Off Road specific notes:
If you live in an area where you can do away with the choke it behooves you to do so. The choke linkage is a dirt leakage path that is hard to totally seal off. I use regular J-B Weld for modifying carbs. The carb absolutely has to be clean for the J-B to stick. Over time the pressed-in plugs in the body can work loose. I put a dab of J-B on each and every plug, being sure to completely cover the plug and a little of the surrounding carb body. I use J-B to plug off all of the various ports & what-not associated with the removed choke.

And now the biggie, Float Bowl Vent mod:
The bowl vent, as delivered, is very suseptable to allowing slosh to enter the venturis. Which make the engine go really rich and blubber.
A note of caution on this mod: it is not a very complicated mod, but it does offer the opportunity to mangle the carb beyond use if not done right. If you need to be shown where the vents are, this is not a mod you should be doing. Proceed at own risk, I accept no responsibility for any mishaps

[vw505]

Thats an old post from a vw page but i have used it on a few webers and it gets them as close as you ever will.

[Mblizzard]

Wow that is some great information. I just quickly read through that but it seems similar to the Weber lean adjust procedure. But it is explained 1000 times better!

Went through the carb tonight comparing what was suppose to be in it stock compared to what is there now. There are so e notable differences that I will post but I have verified that all of the parts are in the correct place. I did note that the primary idle jet o ring had become frayed and some small parts of rubber were on the jet. Cleaned everything and put it back together to see if that was the problem.

What I need to do is pitch this thing and get a new one. But I just hate to think this thing can beat me and I am learning a lot thanks to the posts I have gotten on this. So thanks to everyone.

[Spoke]

For the loss of idle, do you have any intake leaks? You can locate leaks by spraying carb cleaner on any interface (head-to-runner; runner-to-carb). If the tone of the engine changes when you spray the interface, you've located a leak.

[Mblizzard]

I have checked extensively for vacuum leaks but have not found any.

I did break it all back down last night and compiled a list of the factory settings to the current to see if anything was way out of line. Here is what I found.

Part FACTORY SETTINGS Current Settings
Primary Main Jet 1.40 mm 1.40 mm
Secondary Main Jet 1.35 mm 1.20 mm
Primary Air Corrector Jet 1.65 mm 1.65 mm
Secondary Air Corrector Jet 1.60 mm 1.60 mm
Primary Idle Jet .55 mm .60 mm
Secondary Idle Jet .50 mm .50 mm
Primary Emulsion Tube F50 F50
Secondary Emulsion Tube F6 F50
Pump Jet .50 mm .60 mm

For the most part it seems like the same emulsion tube in both the primary and secondary side seems odd.

But the oddest thing is that large changes in the idle volume screw seem to produce very little change in the engine RPM. Which indicates an increase in the idle jet size is indicated. Go to .70 or.80?

Will put the carb back on tonight and see if fuel still drips in to the main.

[vw505]

the rear throttle plate should be fully closed, not even cracked open a little bit. If it is it will act like a vac leak.

[IronHillRestorations]

A couple things I'll add:

Make sure the advance mechanism in the distributor is advancing and retarding smoothly, that can give a major stumble.

The best performing single I ever drove had very small intake tubes, I don't know what the size was, but they were smaller than any I'd seen before and after the owner played with the jetting quite a bit, it ran decent. The single carb set up is total junk in real cold weather, if that's an issue.

[Mblizzard]

The advance is working and I am running the Hot Spark ignition so the timing is pretty much good. If I did not have so many other things to take care of I would just go it FI or duals. I am just hoping to get it to the point of idling well and being drivable while I fix things. But each suggestion is appreciated.

[Mblizzard]

OK I am beaten! Maybe it is just me but I have redone this carb 5 times and it has never been right. Ran a little better each time but never right. So I replaced my pride with my wallet and got a set of dual 44s.

While I know I now have a new set of problems to sort I am hoping that will be more predictable. If not, then I have a very expensive set of carbs sitting on a bad engine.

Anyone interested in a single carb set up with lots of new parts but still won't work? I bet I could make you a deal!

['73-914kid]

what size motor do you have? those 44's are probably gonna be too big...

[Mblizzard]

I hope they are not too big. I have a 1.8 with a big bore kit (96mm x 66mm) = 1911 cc. It is supposed to have a mild carb cam but i have no idea what the grind is. But based on my reading the carbs are at the top end for the displacement but not oversized.

However, given my success with carbs as of late, I will take any suggestions you may have. When it comes to reading about carbs I still have to sound out the big words.

['73-914kid]

the general consensus is that the 44's are too big for a 2.0 liter. the ideal combo for street driveability in my experience is 40 webers with 30mm venturis for a street driven 1911. you may be able to choke down the 44's and install smaller jets to get them to run fairly well, but theres a good chance you will lose some low end power due to the lack of air velocity through the choke of the carb.

who did you order the 44's from?

[Mblizzard]

Got them through Redline. The may not have shipped yet so maybe I will ask for the 40s.