Need Help With Weber Carbs, Won't idle Options

[michael7810]

1972 1911cc with IDF40 carbs, 50 idle, 140 mains, 220 AC jets. Engine & carbs were rebuilt 13K miles ago. Plugs and all ignition parts replaced about 3K miles ago. I have not driven the car much since June, in fact I have not put gas in it since April. My car ran great the last time I drove it about 6 weeks ago. It's finally cooling off in Phoenix so I decided to get it ready for winter driving. So before starting it up I replaced the accelerator pump diaphragms and pulled the float covers off. The bowls were dry and I noticed that 1 of the floats was starting to crumble so I installed 2 new floats, set at 10mm and 32.5mm per the Weber manual. The car started up normal but would not idle. It was running rich (9.0 on the AFR gauge). I let it warm up and it still would not idle, it usually idles fine once the heads heat up to 200F. I adjusted the throttle plate stop screw in a turn to increase the idle and it barely idled, still very rich. i turned the mixture screws in all the way and it idled a little faster but still very rough. The AFR did go up to about 12.0. I cleaned all idle jets and it didn't change. Still the best idle I can get is with all mixture screws turned in all the way. I drained the gas and replaced with fresh Shell premium but that did nothing. It revs OK and runs smooth above about 2K RPM. It seems the problem is with the idle circuit. Is there a way to clean out the idle circuit without disassembling the carbs?
Thanks for any help/suggestions.
Mike

[zambezi]

sounds like plugged idle jets. Pull all the jets (mains too) and try again.

[zambezi]

Idle jets are in the sides of the carbs. don't need to fully disassemble to access them.

[stugray]

Here are my top bookmarks related to carbs:

http://www.weberperformance.com.au/index.p...e2auou15vh6og57

http://www.weberperformance.com.au/pub/Tip...adjustments.pdf

http://www.shoptalkforums.com/viewtopic.ph...15&t=118962

http://www.aircooled.net/vw-carburetors-jetting-102/

http://www.innovatemotorsports.com/resourc...arb-central.php

http://www.webercarbsdirect.com/v/vspfiles...ing%20Guide.pdf

Dont BUY anything from webercarbsdirect, but they have some useful tech info.

[michael7810]

So today I removed the main stacks, idle jets and mixture screws and sprayed carb cleaner thru the mixture & idle jet holes, idle jets and main stacks. Reassembled and it ran much better but not like it was. After adjusting the mixture screws I noticed they were still within 1/4 turn of being turned in fully. So I installed a set of 45 idles (was 50) and adjusted and it runs about the same except the screws are about 1/2 turn out. Since it's drivable I'm going to add some techron to the tank and drive it a few weeks and see how it does. I'm sure all you guys with FI motors are snickering at yet another example of why you should not remove the stock FI. Maybe next winter after I retire I'll install an aftermarket FI.

[euro911]

WTF, you don't look like you're old enough to retire, Michael (IMG:style_emoticons/default/confused24.gif)

(IMG:style_emoticons/default/laugh.gif)

Jets aren't the only places where varnish can build up and clog. There are a lot of passages in the carb body that also need to be cleaned out. Look at small ports in the throat above and below the resting position of the throttle plates. That may be where your problem lies.

I'd pull the carbs completely apart, soak the bodies and your jets in solvent (is Berryman's Chem Dip still available?), then blow compressed air through all the passages, followed by spritzes of carb cleaner through everything and compressed air again.

[porschetub]

So today I removed the main stacks, idle jets and mixture screws and sprayed carb cleaner thru the mixture & idle jet holes, idle jets and main stacks. Reassembled and it ran much better but not like it was. After adjusting the mixture screws I noticed they were still within 1/4 turn of being turned in fully. So I installed a set of 45 idles (was 50) and adjusted and it runs about the same except the screws are about 1/2 turn out. Since it's drivable I'm going to add some techron to the tank and drive it a few weeks and see how it does. I'm sure all you guys with FI motors are snickering at yet another example of why you should not remove the stock FI. Maybe next winter after I retire I'll install an aftermarket FI.

Strange...dropping the idle jets should have made it run worse unrelated to your problem,50 or 55's are the common sweet spot for idle jets for these carbs and the Dellorto's, 45's are getting lean IMO.

Are your throttle plates fully closed when you are setting the mixture screws? try disconnecting the linkages from the crossbar and see if you have more control with the screws.
How clean were the fuel bowls when you were in there ? no water or dirt ? reason I ask is you may have blocked idle circuit galleries for that reason.

[michael7810]

So today I removed the main stacks, idle jets and mixture screws and sprayed carb cleaner thru the mixture & idle jet holes, idle jets and main stacks. Reassembled and it ran much better but not like it was. After adjusting the mixture screws I noticed they were still within 1/4 turn of being turned in fully. So I installed a set of 45 idles (was 50) and adjusted and it runs about the same except the screws are about 1/2 turn out. Since it's drivable I'm going to add some techron to the tank and drive it a few weeks and see how it does. I'm sure all you guys with FI motors are snickering at yet another example of why you should not remove the stock FI. Maybe next winter after I retire I'll install an aftermarket FI.

Strange...dropping the idle jets should have made it run worse unrelated to your problem,50 or 55's are the common sweet spot for idle jets for these carbs and the Dellorto's, 45's are getting lean IMO.

Are your throttle plates fully closed when you are setting the mixture screws? try disconnecting the linkages from the crossbar and see if you have more control with the screws.

How clean were the fuel bowls when you were in there ? no water or dirt ? reason I ask is you may have blocked idle circuit galleries for that reason.

I've ran 45s before with no problems. I have an AFR to keep an eye on mixture and it seems OK.

I'm not sure if the throttle plates are fully closed. I always wonder about this...I open the plates with the stop screw to get the idle RPM right. How can I close them and still get it to idle?? Should it idle with the throttle plates closed? Not sure if there is a "normal" zone but my snail reads 5 at idle on each carb.

I did spray carb clearer around the throttle plate shaft ends to see if they are worn and sucking air and it was OK (RPM did not rise when sprayed with CC)

The fuel bowls were clean and dry when I was in there. I run 3 filters (one at pump entrance and 2 by the carbs) and the tank has been cleaned.

Thanks for all the tips...

[michael7810]

WTF, you don't look like you're old enough to retire, Michael (IMG:style_emoticons/default/confused24.gif)

(IMG:style_emoticons/default/laugh.gif)

Jets aren't the only places where varnish can build up and clog. There are a lot of passages in the carb body that also need to be cleaned out. Look at small ports in the throat above and below the resting position of the throttle plates. That may be where your problem lies.

I'd pull the carbs completely apart, soak the bodies and your jets in solvent (is Berryman's Chem Dip still available?), then blow compressed air through all the passages, followed by spritzes of carb cleaner through everything and compressed air again.

30 years at Honeywell is enough! (IMG:style_emoticons/default/headbang.gif)

[rhodyguy]

Do you own the CB performance weber book? The trouble shooting, symptom, possible cause is invaluable. I would go thru the pre-install procedure.

Is it ONLY running poorly at idle and fine @ 2700 rpm? Try turning the the driver's idle speed adj screw, ONLY, to raise the idle. Now measure the flow on the the front venturis on each carb. They should measure the same. If not, the linkage is out of adjustment. If you're fighting a balky linkage you'll never get anywhere.

[michael7810]

Do you own the CB performance weber book? The trouble shooting, symptom, possible cause is invaluable. I would go thru the pre-install procedure.

Is it ONLY running poorly at idle and fine @ 2700 rpm? Try turning the the driver's idle speed adj screw, ONLY, to raise the idle. Now measure the flow on the the front venturis on each carb. They should measure the same. If not, the linkage is out of adjustment. If you're fighting a balky linkage you'll never get anywhere.

I have the Tangerine cable linkage which is flawless from a sync standpoint. And I have the CB Weber book. I need to make sure the throttle plates are set per the book. For now it's drivable and runs great above idle. It actually doesn't idle bad now just not as good as it ran before the long summer rest.

[euro911]

30 years at Honeywell is enough! (IMG:style_emoticons/default/headbang.gif)

Must have started there when you were pretty young, eh?

Yeah, a lot changes can happen in 30 years. I was still gung-ho up through about year 28 ... then upper management changed everything, and with the new college hires trying to steal my flame, I struggled through 4 more years before I got totally fed up (IMG:style_emoticons/default/dry.gif)

Congrats on your 30 though (IMG:style_emoticons/default/beerchug.gif)

[r_towle]

How is the dwell and timing?