Weber rebuild 101

[pope]

I am going through my first Weber rebuild. Although there is a great thread on tuning Webers, I did not manage to find a comprehensive (for newbies) one for carb cleaning/rebuilding. If there isn't one, then I have a mind to create one . But first I have to go through it once in practice.

Now, quite a while back, I ordered from Germany a Weber rebuild kit. This is what I received:



It is evident that there are some basic things missing from here:
- carb to air cleaner gaskets
- carb to manifold gaskets

In addition, from the disassembly I did on mine and what I have read up to now there may be a couple more things that should be in here:
- gaskets for float bowl plugs
- gaskets for fulcrum screws
Am I correct in this assumption?

Furthermore:
- Where do those white little plastic filters go?
- What are those little plastic curved pieces for?

Also, the PO had o-rings on the idle jet holders:



I cannot seem to find anywhere a reference to their existence.
Should I put o-rings on the idle jet holders when I rebuild?

[deathpunk dan]

My weber rebuild kit came with extra and unrelated parts.
Additionally, the manifold gaskets did not come with it and I ordered those elsewhere. The carb to air cleaner gaskets were not available at the time I ordered, so I simply traced the old ones on gasket paper to make my own.

[911quest]

The filters are for the bolts that go thru the banjo. Where the fuel lines enter the carb(on the side)

[jhelgesen]

I got the PMO rebuild kits for my 46's and they were very complete, but did not come with carb to air cleaner gaskets. Any little bits you need, I'd go to them.

[pope]

Do I rinse the parts cleaner and carb cleaner with water? Or should I just let it dry.

IOW, is it ok to dip the carb in a bucket of water?

(I know I have to blow compressed air into the passages after to make sure there's nothing left in there.)

[shbop]

What are those little plastic curved pieces for?


You're lucky! Those are throttle shaft bushings. I've never seen them come in a kit. If you're going to soak the bodies in carb cleaner, be mindful that these pieces may be on your throttle shaft(s). Carb cleaner will attack them. Be sure to flush with water and blow with air.

[pope]

Great!

Now, when putting the carbs back together again, are there parts that need to be greased, ie the shaft, or the linkage balls? If so, what kind of grease should be used?

How about torque specs? I can't find any anywhere.

[shbop]

I don't know the torque specs, but try to find a copy of "Weber Tech Manual" by Bob Tomlinson. I think www.cbperformance.com is the address. Hope this helps.

[pope]

I have that book. I did not find any mention of torque in it. I'll look again.

[RWebb]

most torque values will be much smaller than any tool you have - unless you have some of those special torque screwdrivers that are used in electronics assembly

there are general purpose torque values (see McMaster-Carr's site) for various materials based on bolt size - again they will be very small

[pope]

OK. I looked more thoroughly in Tomlinson's Weber Tech Manual and I did find some torque specs. It's no wonder I hadn't seen any the first time round - the book has no logical sequence, it's all over the place. Anyway,

for a 40 IDF on a VW engine:

- carburetor to intake manifold nuts: 18 ftlbs
- intake manifold to cylinder head nuts: 14 ftlbs
- velocity stacks to carburetor cover nuts: 12 ftlbs
- linkage rod lock nuts: 2 ftlbs
- shake proof lock nuts: 2 ftlbs

I'll edit this post if I find any more.

[911quest]

"velocity stacks to carburetor cover nuts: 12 ftlbs"

.....that studs is way to small for 12 ftlbs.

[pope]

It says foot pounds and I agree, it looks a bit high. Maybe these nuts are bigger on the IDF's (?)

[911quest]

The only difference is the 40 IDA's use nyloc nuts the IDF's use a regular nut with a lock washer.

[pope]

What liquid should I put in the float bowl to bench test the accelerator pump. I read somewhere that water is not good for the diaphragms.

[pope]

I started with gas but it got too messy, unhealthy and a bit scary. I switched to water.

First I had to manufacture a vial. I bought several plastic 1ml syringes:



I then cut them at the .90ml mark (so they could fit in the barrel without touching on the butterfly) and burned the tip so it would seal. I pierced through the syringe at the top with the needle and bent it so that it could serve as a handle. I bent the other side round so I wouldn't punch a second hole in my finger



If you're going to be using gasoline (or a solution that erases the markings), make sure you cut it near the 80ml mark so you can gauge without having the markings.


I proceeded to fill the float bowl with the accelerator pump intake valve with water (I left the float inside). I depressed the throttle lever several times until the accelerator pump jets were squirting normally. I refilled the float bowl with water (up to about a cm below the top of the carb).

I then took measurements from each jet in the following order: 1 - 2 - 3 - 3 - 2- 1 - 2 - 3 - 3 - ... I repeated for the second carb. Here are the results:



What this tells me is that the differences between jets per carb are insignificant. The next step will be to calibrate the jets for cylinders 2 and 5 to 0.75ml with gasoline when the carbs are back on the engine.

Do not forget to empty all the water. Remove float, float bowl plug, accelerator intake, emulsion tube, idle jet, main jet and the whole accelerator pump system. Put carb on radiator to dry and blow compressed air through all the passages linked to the bowl that was filled with water. Take extra care to dry the pump diaphragms well.

[pope]

OK, I put the carbs back on the car. After running through checks 5 times, I ran through checks another 2 times. I finally started the pump.

All was going well until I started to hear dripping. Drip drip drip drip. I quickly switched off the pump. I realised that the barrel of cylinder one was filling up with gasoline.

After removing the carb cover I found that I was stupid to trust the default setting of the float tab of the new float I installed to replace the damaged one. It was unfortunately lower than the tabs of the other floats. I have now adjusted it accordingly, have put it back in and am about to switch the pump back on.

I assume that all will be well now but my question is: there's a certain amount of gasoline in the cylinder now that seeped past the butterflies. Some of it was slowly dripping out of the throttle shaft too. Will there be an issue when I start the engine?

I left the pump on for about 30sec, probably less. The gas in the barrel over the butterfly was about 1/4 to 1/2" deep at its peak (it kept dripping in there after I switched the pump off).