TheSamba.com :: View topic - Stock jets for a 30 pict 1 & 28 pict 1 carb?

Mon May 01, 2006 8:54 am

trying to set up the mixture on my judson at the moment, just wanted to know the stock jet sizes for the above carbs :)

thanks in advance 8)

Mon May 01, 2006 10:03 am

I have heard that you have to go with a slightly bigger jet when you use the judson. But I have never set one up so...

Based on alot of carbs I have rebuilt/torn down over the years...

I think 28 picts had a 112.5 or 116

and the 30 a 116 or 120... maybe I have even seen an odd 117.5

and I have seen 122.5, 125, 127.5 which are more likely 30 pict 1 -34 pict jets.

Maybe Bill May or some one else has some more exact "what they came from the factory" with info.

Mon May 01, 2006 10:05 am

I would think the jet sizes need could be found on the judson registry:
http://vwjudsonregister.tripod.com/installation_page.htm

Mon May 01, 2006 10:23 am

yes i am a regular on the judson forum, but what with different grades of fuel here in the uk to what you guys have in the US and i am also running a 30 pict carb instead of a stock 28 pict one means i will have to play about with the mixtures.

just wanted some factory jet sizes to make a start from, and then work my way up :)

Mon May 01, 2006 11:20 am

28pict-1
main jet 122.5
pilot jet (idle-) 55

30pict1
main jet 125
pilot jet (idle-) 55

Mon May 01, 2006 11:46 am

thanks :)

8)

Mon May 01, 2006 12:32 pm

not to sound dumb here, but to just check, i am right in thinking the larger the main jet the richer the carb mixture is?

so a 125 jet will be leaner then a 135 jet?

Mon May 01, 2006 2:00 pm

Right the smaller the # the smaller the size of the jet orifice.

Mon May 01, 2006 2:07 pm

The size of the jet is based on flow measurement, so yes, a larger jet means more flow.

By the way, the 1500 engine actually had a smaller main jet on the 30PICT-1 than the 1300 did. However the 1300 30PICT-1 did not have a functional high speed enrichment system, and the 1500 did. I have a NOS Bocar repro of the 30PICT-1, which has the high speed enrichment, and the jets as shown below for the 1500. I'll also include the air correction jet - the letter after which is the emulsion tube, and Ghia carbs usually had a larger a/c jet.

1200 28PICT/-1:

Main 122.5
Pilot g55
Air Corr: 130y

1300 30PICT-1

Main: 125
Pilot: g55
Air Corr: 125z

1500 30PICT-1

Main: x120
Pilot: g55
Air Corr: 125z

-Andy

Tue May 02, 2006 4:37 am

Rob,

Further to what we were saying on The Judson Forum I don't think what you have been running on your 30pict (135 main jet) is a bad starting point.

Yes, black and sooty means you are rich but better rich than lean with a supercharger.

If you want to lean out the mixture a little then go to a smaller main jet. I'm not sure what's available but ask some of the carb experts here and reduce in small steps.

Always check the colour of #3 plug first after each reduction in jet size and use that as your benchmark because, as you know it always runs hotter anyway.

Tue May 02, 2006 2:52 pm

hey thanks for the replies and thanks john :)

well i was talking to my buddy at the volksworld show and hes a good mechanic, i told him my mixture was too rich, so he suggested starting with stock jets again and working my way up.

Ive tried both 135/130 jets as suggested by Gelhaar but i guess the gas quality in the states is different to the uk as both those jets made the engine run far too rich and i didnt want to risk washing away my rings :shock:

so i put a 125 main jet and a 55 idle jet and it seems to run sweet at the moment, and the tail pipes arent too black at the moment, but i need to put some miles on it first and see 8)

thanks for all the advice 8)

Tue Nov 15, 2022 7:54 am

to ask even a "dumber" question than the one above, if a richer means more fuel and the jets let in air, why wouldn't a larger jet result in a leaner mix?

Which of my assumptions is wrong?

Please have patience with a non-mechanic ;)

Tue Nov 15, 2022 2:36 pm

Dmangold wrote: Which of my assumptions is wrong?

The assumption: "and the jets let in air,".
They don't. Jets let in fuel.

Tue Nov 15, 2022 3:41 pm

simple enough - much appreciated!!!

Tue Nov 15, 2022 10:48 pm

With one modifier here, the main jet and idle fuel (pilot) jets are for fuel flow.

The air correction jet, on the other hand is for... wait for it... air, that gets mixed with the main jet fuel flow at higher engine speeds.