Weber IDS circuits clogged again

[1968SWTs]

Weber IDS carbs - 68 911S
Gas tank has bean cleaned, fuel filters everywhere. Looks like paint from air cleaner got to bowl. Question is what is the most efficient way to clean the low speed / idle circuits.
Carbs were recently "rebuilt" by Bieker - but that was a huge mistake, but everything was running perfectly after the last cleaning. ( I suspect his "plating" process generates crap in the passages)
I am looking for a more efficient procedure. Car now runs great with the high speed circuit or under great load, but sputters like crazy transitioning from idle unless full throttle. Idle has pops as well.



thanks in advance for any advice

[howard freeman]

What does the inside of the fuel tank look like? Pull the sending unit out of the tank,take a small inspection mirror & flashlight or a borescope & have a look @ the upper part of the tank. Bet you will find rust & that will constantly cause the carb jets to clog.
Howard

[1968SWTs]

thanks - I will do that
for now I want to get the passages cleaned on the carbs
not sure why it is not working this time

[howard freeman]

I also see your 180 air correction jet in the photo is stopped up with rust. Use Berrymans B12 Chem tool & air to clean the jets & passages. I would sugest you remove the air correction jets & emulsion tubes under them & clean that entire circuit as well as the main & idle circuits. What type fuel filter do you have?? I use a Mahle KL9 from mid 80's bmws for my carbed 911's.

[1QuickS]

I believe there is glass bead in some of your fuel galleries. Most can be flushed with Berryman's and a long nozzle; spray all passageways, they are easy to isolate and spray.

There is one passageway that isn't directly accessible; but the following procedure will help blow it clean:

• remove emulsion tube but replace air correction jet
• pull idle jet
• close mixture screw
• leave transition port plug in place
• remove main jet assembly
• remove secondary venturi
• insert the rubber eraser from the end of a pencil into the main jet well and secure it in place with the main jet carrier (lightly seat it but if it gets stuck then compressed air will remove it later)
• blow compressed air into the idle jet well
• watch for debris to come out of the transfer port where the fuel would enter the secondary venturi (wear safety glasses)

[1968SWTs]

thank you for the replies!

I found part of a technique by accident - backing out the idle jet housings will kill the motor if something is wrong, i.e. the 5mm rubber o-ring compromised
sort of a delayed reaction

[1QuickS]

O-rings on idle jet holders are not to be used on early throttle bodies for this reason. Hope this was the issue...Lean Best idle adjustments can't be performed correctly if idle jets don't seat...idle mixture becomes impossibly rich as a result.

[1968SWTs]

Thanks Paul for the detailed procedure. That makes sense.
By the way, I went to Beiker Engineering in April 2011 because I was told 30 days.
the Performance Oriented schedule stated nothing until after July at that time, but I have since learned your schedule is very honest and conservative. I think I waited 8 months for what was promised in 1!
And thanks for the last response. I was told by someone else they weren't needed. Not sure why they were installed . It sounds like the holders "seal" without even a washer, (or there is no need for a seal), and that the o rings were creating a gap where the idle jets should have been seated.

[1QuickS]

The o-rings were added as a design revision for the Webers starting in 1969 (IDTP series) and I assume they were added to help control unwanted air into the idle/progression circuit. There are modifications to both the idle jet holder and to the casting/machining of the throttle body to accept the o-ring there and the idle mixture screw adopted an o-ring seal which is located under a special washer and is sandwiched between the throttle body and the spring around the screw.

The typical rebuild kit includes these 12 0-rings to use when rebuilding the later Webers but should be tossed when rebuilding the earlier versions. Your example is what happens when the o-rings are installed onto the earlier throttle bodies; the potential for poor seating of the idle jet can occur.

By the way, if your throttle bodies were bead blasted then you may want to consider applying some steel conversion coating to the studs and vent pipes to help prevent rusting due to the loss of their zinc coating from blasting, assuming they weren't protected during the process.

[1968SWTs]

thank you Paul!

removed the thin O -rings and everything is perfect - not a single pop - starts instantly when cold - drives as smooth as a showroom new EFI car.

Jet housings must be properly seated - of course. I would have needed X-ray vision to see that.

You saved me a LOT of time and frustration.

This also proves my point. I have often been told that an opinion by a shop, parts seller, kludge retrofit hobbyist turned aftermarket supplier, engine builder, etc. has to be gospel because they are the experts because they "have been doing it for years" or everyone uses them for the expensive builds, etc. How can someone (the other Weber rebuilder) who has been doing it for 50 years deliver these with such a major error? How many other showroom 911S SWB's are out there with O -rings? Anyway, thank you for not fitting in to that category.


This is the THIRD case where the "expert" was way off base and many follow the expert. The engineers in the 60's actually did some engineering!

Thanks again for making my day.

Dave, Marco, Lyle, Scott, Gordon, Ed: you are in for a treat!
Performance Oriented Terms

[howard freeman]

Originally Posted by 1QuickS

I believe there is glass bead in some of your fuel galleries. Most can be flushed with Berryman's and a long nozzle; spray all passageways, they are easy to isolate and spray.

There is one passageway that isn't directly accessible; but the following procedure will help blow it clean:

• remove emulsion tube but replace air correction jet
• pull idle jet
• close mixture screw
• leave transition port plug in place
• remove main jet assembly
• remove secondary venturi
• insert the rubber eraser from the end of a pencil into the main jet well and secure it in place with the main jet carrier (lightly seat it but if it gets stuck then compressed air will remove it later)
• blow compressed air into the idle jet well
• watch for debris to come out of the transfer port where the fuel would enter the secondary venturi (wear safety glasses)

Great Idea Paul, Will try that next time I have some badly plugged carbs.
Howard

[larrym]

very VERY carefully - no more than 15 psi - pull the idle screws and blow back thru

any more psi will collapse your floats

it works - btdt

.

[1QuickS]

Floats will collapse when high pressure air is introduced into the fuel line and the top covers of the carbs are in place.

The procedure I presented directs the air through the fuel gallery that supplies the idle jet from the bottom of the emulsion tube well; the continuation of this air path as described is up through the air correction jet and out of the transfer port to the secondary venturi. The path to the float well is blocked with the eraser tip inserted into the main jet receptacle. As such, there is little chance of the float being damaged.

Of course, it is understood that the clearing of fuel galleries would be a task best performed with the carbs on your bench and disassembled to some degree; inclusive of removing the top cover of the carb body to have access to those fuel galleries under the top cover.