Instructions for changing jets on a Weber DGES



Hopefully some of you vets can fill me in on this one. I bought a jet kit from redline and it includes idle jets, main jets and air/corrector jets. I know my carb is jetted too small because I had to back out the mixture screws too far to get it tuned. So do I just put in a larger main or go up one step on everything.? Or should there be a set relationship like idle50/main150/air190 or idle55/main155/air200 which is the way they are organized in the box.?

Also are there any step by step instructions out there for changing the jets?

Carburators are sort of the last frontier for me I have learned pretty well how to do everything else, but I have note yet gone inside a carburetor so I am a little wary.

Just because you had to back out the mixture screws a lot to get it to idle doesn't necessarily mean anything other than you may need to install larger idle jets. There is a brass plug with a slotted head on each side of the carburetor next to the venturis. These house the idle jets. I ran a 50 primary and a 70 (drilled out even larger) secondary idle jet. Start by removing the plugs and seeing what you have first.
I thought that the Red-Line kits came with instructions? I know that most of the Weber suppliers out on the web, like Red-Line, have the carb tuning instructions.

I would have to go back and look at my notes to see where I ended up as far as the "Idle Jets" size. To start with I didn't even mess with the Main Jets. According to the procedures published on these sites the emulsion adjustment (idle screw) should be out no more than about 1.5 to 1.75 turns. If the turns out are greater than 1.5 to 1.75 than the orifice size of the Idle Jet needs to be increased.

I found a DFV at a garage sale that had been used on a VW bug. After rebuilding I started out at 3.25 turns out for a good idle. After increasing the size of the Idle Jets in increments I am now sitting at approx. 1.75 turns out.

I used a set of the small drill bits to gradually increase the size. Were talking bit sizes like .0052, very small.

The kit 701DGV6 (six cylinder) from Carbs Unlimited included the idle jet sizes 70, 80 and 85. Come to think of it, I think I ended up at the equivalent orifice size as the 70 or 75mm Idle Jet. Start with the smallest and work your way up.

Good luck, Ric.
Yes I have the tuning instructions. That is how i figured out i needed to install a larger idle jet. My coinfusion comes from the fact that the jet kit I ordered has main and air corrector jets also. It sounds like you both agree that I need larger idle jets. But what symptoms would lead me to install a larger main or air corrector jet?

Other than the lean at idle my car runs good but when I punch the gas pedal it bogs down a bit before taking off. . . is there a jet change that will fix that?
The bog sound like you aren't getting enough of an squirt out of the accel pump. As far as the main jet you need to read your plugs after running. Not knowing what jets that came in you kit, I would bet that the smallest jet is larger than the one that came in the carb. Start with that one and increase the size until you get that nice light tan color.

Good luck, Ric.
What dizzy are you running?

I too have a 38 DGES. I know for a fact that I need larger idle jets, but I think everything else is OK. Let me know what you end up doing to everything.


I have the very typical 200 with a 38dgas, a Duraspark II distributer, MSD 6A, and Clifford 6-2 header. There must be 100's on the forum with the same. Jason, I'll let you know what I end up at for the idle jet.

I'll fix that first then try to eliminate the bog off the line, if I am not getting enough out of the accellerator pump how should I fix that? The carb is brand new by the way so it shouldn't be worn out just needs tuning.

I think there are only a handful of us with 38 DGES's. A few more have the 34/36 DGV, but not many really. I tried to find some info out a while back and the only a few people ended up being any help. Lbones and John are 2 that I can think of right now.

My car runs a ton better now that I have a D2 setup. I need to rerun the vacuum plumbing and get some manifold vacuum, but no biggie there.

Keep me in touch and we can work these things out together. From what I understand, Clifford supplies them, but at a base set-up which is more for a really hopped up bug.


Just a thought. The 38 is a lot of carb for a stock engine (350cfm). Also, it is not progressive, so you have 3" of full time venturi (stock was 1.10"). The bog you are experiencing could well be too much fuel at tip-in (off the line). Don't be afraid to back down on the idle jets as they control tip-in and transition fuel ratios. The info on the Clifford site Doug refers to is very good.

I've thought about that, but I am way out on the idle screws. Redline weber suggests no more than 2 turns. I am out a little over 3 right now. It idles great and runs awesome once the tranny shifts down. I need to adjust the kick down for sure.

Well, I got ythe Hayes manual from Amazon on Weber carbs so at least I now know where all of the jets are. I hope to put in bigger idle jets this weekend and check the numbers on the main and corrector jets. I'll keep in touch.
Let me know what you get for all your jet numbers.. I would like to compare and make sure that we both have the same base line.

If you need any help in taking the buger apart, you can email me directly at

Have fun!
Well, I got in there finally. I found 45 idle jets, 142 main jets and 185 air corrector jets. I decided to try 55 idle jets first and it tuned up just right with the mixture screws backed out one full turn. So that seems good. I haven't driven it enough to see if the hesitation at launch is gone now.

I will look into ordering a few idle jets and see what I can get!

Thanks for the update!