So you want to rebuild your Webers?, Here is how I did RoadGlue's Weber 40 IDFs. Options

[ThePaintedMan]

Awhile back, Randy (RoadGlue) gave me the opportunity to rebuild his Weber 40 IDFs, and I thought I'd take the opportunity to document the process. I'm also going to try give a little insight on some of the tips and tricks I have learned along the way. Keep in mind, this thread is a work in progress, as Randy and I are still tracking down some of the parts these carbs were missing.

Now, I understand for most people, the process is fairly straightforward and many of you will think it unnecessary to give a step-by-step. After all, most rebuild kits only include a handful of parts and the location and function of most pieces are obvious. But there are some important additional steps that one can take to truly ensure the rebuild process goes smooth and that you won't have to do this over again immediately after reinstalling the carbs.

Here it goes!

First, I would like to outline the fact that not all Webers are the same. Not only are there different models of IDFs (the 36, the 40, the 44 and the much rarer 48), but there are "early" style carbs and "later" ones. I'll try to list some of the most obvious differences, which are to the best of my knowledge true in most cases, but may not hold true in all of them.

Here are the tools you'll need for the job:
-Carburetor rebuild kits (CB Performance or Redline are the most common)
-8mm open/closed end wrench
-10mm open/closed end wrench
-11mm open/closed end wrench
-19mm open/closed end wrench
-Smaller flat tip screwdriver
-Large flat tip screwdriver
-Brass brush
-Paint gun brush cleaning set
-Small hammer
-Brass punch set
-Razor blade
-Carb cleaner
-B-12 Carb dip
-Anti-seize
-Shop towels
-Compressed air source (preferably)
-Clean workspace, preferably with white background

Optional:
- (4) 3/8 x 24 Brass Hex grub/set screws
- Allen keys
-SAE Tap and Die set

Below is a picture of an early and late set of Weber 40 IDFs.



Some of the characteristics of EARLY versions are:
-Short emulsion tube holders
-Short throttle shafts with little overhang outside of the carb body
-Non-sealed, ball-in-cage style throttle shaft bearings
-Cam-actuated, non-adjustable accelerator pump assembly
-No ports for "ported" vacuum (still has 2 "manifold" vacuum ports)
-76 degree bevel throttle plates (this may or may not hold true for every set of early carbs)
-No throttle return springs installed from factory (thanks Kevin for clarification)
-Most (all?) were made in Italy and are stamped as such


Later style Weber 40 IDFs (Weber 40 XEs) are usually characterized by:
-Taller emulsion tube holders which extend above the carb top
-Longer throttle shafts
-Sealed black throttle shaft bearings
-Adjustable, spring cushioned accelerator pump assembly
-One pre-drilled ported vacuum port in addition to two threaded manifold vacuum ports
-78 degree bevel throttle plates
-Factory installed throttle return springs
-Made in Spain, but potentially also Italy and Brazil


Please note that most of these instructions to follow are also true for 44s and 48s as well. The main difference being the way that the secondary venturis are designed.

[ThePaintedMan]

The best way is probably to use an ultrasonic cleaner, which will not only clean the corrosion on the outer portions of the carbs and throttle bodies, but will also remove scale and corrosion inside all of the small passageways. Unfortunately many of us don't have access to such a machine (although it's in my plans). Therefore, I decided to go a little different route with Randy's carbs. Below is another shot showing the deposits and oxidation in the fuel bowls.




.... And all of the stuff that fell out when they were turned upside down. Now aren't you glad you're rebuilding your carbs?



First, strip the carbs of all removable parts, keeping everything in baggies as you go. It's not if lose you lose a part, it's when. And tracking down individual replacement parts for Webers is not only a pain, but it will quickly drive up the cost of your rebuild and keep you off of the road longer.



**However, DO NOT, unless you deem it absolutely necessary, remove the throttle plates or shafts. Bob Tomlinson, in his Weber Tech Manual, specifically recommends avoiding removing these parts from the carbs because realigning the plates and shafts exactly as they were pre-rebuild is nearly impossible. Not to mention the process of driving out the old shaft(s) will likely render them bent, giving you a whole other set of variables to deal with (ask me how I know). In some cases, where the throttle shafts and/or bearings are seized in the bores, you will have no recourse but to remove them. In this case, make every attempt to mark and maintain each butterfly with its parent throttle body as, like most parts that wear, each fits in it's position in a unique way over time. **

Ideally, the next step would be to dip the carbs in cleaner to begin braking up all of the gunk that has built up on them over time. However, there is a reason why that may not be the best idea. Remember those throttle shaft bearings I spoke about - the sealed ones? Well, they're not perfectly sealed. And if you submerge them in something like B-12 Chemtool, you're liable to dry out and destroy those bearings, meaning you'll end up having to pull those throttle shafts afterall. Instead, what I did was to clean the outside of the carb with a good dousing of carb and/or brake cleaner, being careful to avoid the shaft bushings. Baste or pipette B-12 or other good carb cleaner into the fuel bowls and let that soak for 2-4 hours. As you can see below, if you are careful and keep the throttle plates closed, you can even soak the top of the butterflies if they seal well enough. Soak all of the parts you removed in B-12 at this time too. I like B-12 because it seems to do a better job breaking down hard deposits than the stuff you get in the can.