Weber 38 DGAS needle valve size (1 Viewer)

[MTCO60]

I purchased an 84 fJ60 from my Uncle in Montana a couple of years ago. We trailered the rig back to CO, and I finally have some space to work on it. So far, I have boiled the rusted gas tank and relined with red kote, changed plugs, wires and oil. This site has been amazing and provided endless information and resources. I’m thankful for everyone sharing their knowledge with us novices.

This weekend I removed the Weber 38dgas from the desmogged 2F for a rebuild. I have changed the idle, main and air jets based on a post from @Dizzy (elevation in Nixon MT is 2100’ vs 5280’ Denver). The rebuild kit I got has a 1.75mm needle valve, replacing the 2.50mm that was installed.

After doing some research, I found the original needle valve for Weber 38 is the 2.50mm. I have rebuilt the carb but haven’t installed it yet (waiting on a single gasket I was shorted in a kit). Should I put the 2.50mm valve back in?What will happen if I leave the 1.75mm installed?

Any feedback is much appreciated. Here are some pictures of the rig and the work completed. Thanks!

 

[Dizzy]

The rule of thumb is to run the smallest needle and seat that you can without the level in the bowl being affected. Fuel pump fuel volume and pressure that is great will overfill a bowl. But if the needle and seat valve aperture is smaller, and the pressure correct, it will not be of significance.

So, in general, the bowl level determines the level of air/ fuel in the emulsion tubes, the higher the level, the richer the emulsified mix will be in the idle and main circuits.

Your float level, your fuel pump and plumbing configuration, ect. can all have an effect. I wouldn't be concerned unless you experience a lean condition.

 

[MTCO60]

The rule of thumb is to run the smallest needle and seat that you can without the level in the bowl being affected. Fuel pump fuel volume and pressure that is great will overfill a bowl. But if the needle and seat valve aperture is smaller, and the pressure correct, it will not be of significance.

So, in general, the bowl level determines the level of air/ fuel in the emulsion tubes, the higher the level, the richer the emulsified mix will be in the idle and main circuits.

Your float level, your fuel pump and plumbing configuration, ect. can all have an effect. I wouldn't be concerned unless you experience a lean condition.

Awesome. Thank you for the info. Prior to pulling the carb, it was running rich. The Jets were 55 idle, 140 main and 180 air. I went with 50/140/190.

 

[Dizzy]

Are you using a stock fuel pump?

 

[MTCO60]

yes I believe it is stock. There is also a fuel regulator installed but I’m not sure where that should be set.

 

[Dizzy]

3lbs.

Did the regulator get a taste of the rusty tank?

 

[MTCO60]

3lbs.

Did the regulator get a taste of the rusty tank?

okay thanks. The regulator has seen rust. My uncle could run it down to a half tank, then the gas tank pickup tube would start collecting rust. The fuel filter would clog and the rig would stop running.

when I took the carb apart, the screen was stained with rust and the bowl had rust in the bottom. Fuel pump and regulator have not been changed.

 

[Dizzy]

Fortunately, a Weber bowl is easy access for inspection. I'd consider carrying a section of fuel line to bypass the regulator if it gives you trail/trip trouble, because many Mudders run Webers without regulators (even though it is probably too much pressure).

I plan on eventually running a Weber on my Cruiser's 2F. Doing it for really high altitude, and an accelerator stumble that won't go away without bolting my 32/36 DGEV on the manifold.

I bought an electric pump from Cruiser Corps that requires no regulator and can deliver sufficient volume, according to them. I currently have a brand-new factory pump on my '75 2F with the stock carb, but I don't like the idea of a gas leak finding its way to the crank case, so I'll eventually install the electric pump regardless of carb.

 

[MTCO60]

I’ll definitely do that. Thanks again for all the info. Gasket should be here mid week and I’ll hopefully wrap this up. Not much else to do while sheltering in place. Did I read somewhere that you’re in CO or am I making that up?

 

[Dizzy]

I'm in Santa Fe, eight hours away. My folks are from Colorado. The last time I was in Colorado was last August, at the Great Sand Dunes National Park.

Who is your supplier for Weber parts? Post up a pic of the engine bay when it is all done.

 

[MTCO60]

I'm in Santa Fe, eight hours away. My folks are from Colorado. The last time I was in Colorado was last August, at the Great Sand Dunes National Park.

Who is your supplier for Weber parts? Post up a pic of the engine bay when it is all done.

I’ve lived in CO my whole like and never been to sand dunes. Will have to make the trip this summer.

I purchased the rebuild kit from “best supplies” on EBay. Supposed to be legit redline but I’m a little skeptical since they shorted me gaskets and the power valve seal. Not well packaged either. They are sending a second kit this week. The jet kit came from eBay as well and that was good. Sealed in the redline box.

Here are pics of it rebuilt. Will send some more of the engine bay after installation

 

[mano002]

When I set up my weber 38 on my 22R, there was very specific instructions on how to set-up the idle jet size to ensure you aren't starting to open the butterfly valves at idle. LC engineering has all of the jet sizes and when I bought my carb, I bought the kit with all of the jet sizes.

 

[MTCO60]

When I set up my weber 38 on my 22R, there was very specific instructions on how to set-up the idle jet size to ensure you aren't starting to open the butterfly valves at idle. LC engineering has all of the jet sizes and when I bought my carb, I bought the kit with all of the jet sizes.

Thanks. I did notice the instructions for tuning are very specific. I think I’m grasping but will know better once the carb is in place. The jet kit I bought has 50/55/60 idle jets 150/155/165 main and 190/200/210 air corrector

 

[MTCO60]

Okay so I got the carb reinstalled and tuned as best I could. Started at baseline. When I adjust the mixture screws, there isn’t much change from 1/2 to 3+ turns out. If I close them down, engine sputters and dies. Even when I have the mixture screw 3 turns out, it seems to be running rich based on the odor.

I’m thinking I should change from 50 to 40 on the idle jets? Any advice for what could be happening? I’d like to wrap this up tomorrow instead of waiting for smaller idle jets.

I did check for vacuum leaks with carb cleaner and didn’t hear any audible difference. Throttle response is very good. Adjusting timing tomorrow. Any advice is much appreciated!

 

[Dizzy]

The mixture screws will have little influence if, they are too far out, or if the idle speed screw has the throttle plates too far open. The idle speed screw should be about 1/2 turn max on the 38/38. First thing I'd check is that you can idle at about 600 rpm (or where it is smooth) with the speed screw about 1/2 turn in. @JohnnyC has a suggested guideline for jetting this carb at altitude, IIRC.

 

[MTCO60]

The mixture screws will have little influence if, they are too far out, or if the idle speed screw has the throttle plates too far open. The idle speed screw should be about 1/2 turn max on the 38/38. First thing I'd check is that you can idle at about 600 rpm (or where it is smooth) with the speed screw about 1/2 turn in. @JohnnyC has a suggested guideline for jetting this carb at altitude, IIRC.

When you say 1/2 turn in on the idle speed screw, you’re saying 1/2 turn past contact with the throttle stop lever?

 

[Dizzy]

Yes. But, I suspect that it will be more - which isn't correct. But, as long as you aren't running lean or rich across a full range of throttle, you aren't running ported vacuum advance, and your idle rpm is more or less consistent, I don't see a major problem.

The same, or similar, issue presents itself with the Aisan carb, but the Toyota solution is to get the engine (and/or manifold vac) back to operable spec, or buy a high-altitude model. Most Mudders wouldn't even identify it because there is only a rpm specification for the idle speed screw. There is one other trick to making the tune correct, but it involves drilling a 1mm hole in the throttle plate, opposite the progression holes - which I did on my Weber, that is installed on my Nissan, and, on the Aisan in my 40.

 

[MTCO60]

Okay so I decided to adjust my float level and then took the whole carb off. Found a few things. Bolts holding the flange to the manifold are too long as discussed in previous threads. I hadn’t seen any pictures of that scenario, so I added those.

The confusing one to me is regarding the throttle plate. I thought the edge of the plate should cover the progression holes when throttle is closed. The plates close 100% but mine don’t seem to to cover progression on one side. Is that normal? Can I adjust throttle plates?

 

[MTCO60]

Here is a video. Maybe I’m not understanding the sequence of progression ports. I thought both sides were supposed to cover with edge of plate.

 

[Dizzy]

I see what you mean. There is backlash in the gear teeth, nothing to worry about, until you start getting physical wear in the throttle body, or the throttle shaft gets excessive play.