Leaking throttle shafts picture..

[Old H2S]

After the first cleaning you can see the pattern on the bottom of the bores at the shafts.

[930cabman]

We have a set of these (Weber 40 IDT 3C) in the shop now. What is the procedure to measure/check the bores/shafts?

[Old H2S]

Enjoy Paul Abbott's website..down the rabbit hole.

Performance Oriented

[930cabman]

Thanks, I have been reviewing this information for the past week still have yet to find a procedure for checking the throttle plates.

[Old H2S]

First you must remove the screws and that needs a Dremel tool and a rotary bur to cut the backs of the staked in screws. The screws must spin easy, easy, easy. Any torque on them and the shafts will bend and you will never get them out, they are very soft. Pull out the throttle blades and they are even softer- brass without damaging the edges, they are cut on an angle and the slightest nick and they will not close all the way you will never get all 6 bore to idle the same. Then comes the reboring the housings for larger bushings. Run the shafts in a lathe to clean up burrs and straighten them out. Cut the new bushings undersize and ream to a "neat slip fit" for the shafts.
Over all you can see this is a huge PITA and the reason the pro's charge 3-4k to rebuild them.
Look on YouTube for some vids and look at the other thread here now about Weber back firing problems and the problems I found. The second carb I started today and it does not match the first one according to the series numbers, plus someone must have used a hammer on it ???
Throttle plates you check with a light beside the top of the carb and look at the lock up on the blades, the center one was out of alignment on both carbs and required VERY CAREFUL edge burnishing to take care of the nicks and dings that were holding it open and the edge off angle must be kept the same or the opening will get bigger not smaller. All the mating surfaces were off a lot. A granite surface plate is the best tool for many of the checks and repairs. Harbor Freight has them for less than 100.00 but you have to go pick them up.
So the Porsche God calls me up last night because he read the other thread and says don't forget to check this ,this, and this.. Crap all of those surfaces were off by a more than was obvious.
The first one I ultrasonic 10 times and the "hidden passage" was still full of crap on 2 of the bores, these things are a time eater, I must have 16 hours on them so far.

[930cabman]

Thank you for the repair procedure, is there a method for checking prior to dis assembly?

[Old H2S]

I think Al said it best on the other thread.. wiggle the shafts when the engine is running and see if the RPM changes or starts to stumble and pop.

[930cabman]

Originally Posted by Old H2S

I think Al said it best on the other thread.. wiggle the shafts when the engine is running and see if the RPM changes or starts to stumble and pop.

I would like to believe the Germans could do better than that, but wait a minute, it would be the Italians. That explains it.

[Old H2S]

Unless someone bought a new set, all the Weber's are old and still TOO expensive for what a mess you end up with.
Here are some HACKS to try..
Do not remove the shafts, get the grease gun for the tip of your chain saw blade with the little tip and drill a real shallow hole in the side of the housing where the shafts come out and pump it full of grease to help seal it up. Will it work? is it right? Will it stick in the winter? Is it better than a 3000.00 rebuild for a little of your time? Most of these carbs are 60 years old. Will the Karen's scream? Yes.
Another hack is setting the float heights which have a silly tolerance to hold, they all MUST be the same, good or bad, right or wrong. They control when the main circuit starts at what RPM. They make a little bridge gauge to set the float, BUT you must hold the float up while you push the gauge down and then measure the tang that the inlet valves relay on for stopping fuel flow. This requires 4 hands, the wife was not happy. So I made a shim out of a chop stick that I can wedge behind the float to keep it in place while you measure the tang height to a silly tolerance of .004" I used a base adaptor on the bottom of my caliper to get this right. One set of carbs was pretty good but the other set was way off so the transition from idle to mains was a mess. Whether you get settings right or wrong is one thing but you want both sides the same so you can tell when the fuel curve needs adjustment to both sides.
Right now I am looking at QuadSeal "O"rings on McMaster-Carr to put on the shafts to help seal
them up, yes it is wrong but to do a good job on shaft bushing replacements you really need a milling machine and mine is 350 miles away from here.
Flame on gents..

[Dpmulvan]

Originally Posted by 930cabman

We have a set of these (Weber 40 IDT 3C) in the shop now. What is the procedure to measure/check the bores/shafts?

You can usually visually inspect the bores to see how much the plates have cut into them if the bores do have damage you can cut them oversized with a a boring bar in a milling machine and buy oversized throttle plates. To check shafts, Unless the carbs are on a running motor the only way to check them is to remove them and measure them. At the price of used Webers I would just spend the money on the parts and do a full rebuild. Helps to have a wet blaster only way to remove all the crud.

[Old H2S]

Yes I'm a heretic. Searching for better ways of problem solving, but really? This is what Weber gives you as a shaft seal..
A mere scrap of teflon tape they wrap around the 2 end shafts? What about the middle bore? Nothing. Both middle bores on each set were the most damaged, both shaft wise and butterflies not closing or in sync. Teflon is soft and it cold flows badly, fast, pulling out the old teflon "seal" and putting in a real "O" ring would be better but there is still no love for the middle bores. This is why the pro's get big money to rebush all 6 leaks on one shaft with brass inserts.

[Old H2S]

Sorry pic did not go through.

[Old H2S]

Done and gone..
Parts came in Friday, built and triple checked everything. Owner will install tomorrow and I know it will run better after fixing all the leaks and clogged passageways. Thanks for your comments.

[Old H2S]

I helped stuff the engine this morning, owner just called and said that it started right up and idled at 1000 RPM no adjustments needed.. He will do the dial in on the idle mixture screws tomorrow.

[Old H2S]

He brought the 914 over to have the ignition timing checked, said it was strong down low but ran out of power at high RPM. I checked and max advance was 15*
Set it to 34* and all horses are accounted for and he says it's too fast.