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]

Now move on to the accelerator pump cover.

Note that there are two style of pump covers and associated diaphragms. If your carbs have and adjustable pump lever rod (pictured here) then you will use the diaphragm in the kit that only has a metal face. The one with the white button on top is used with earlier style carbs with a non-adjustable lever rod.



First place the diaphragm on the pump cover. I like to thread the screws through the holes in the diaphragm first to locate it correctly and prevent the rubber from being pinched or the seal leaking upon installation.



Finally, place the spring on the recess in the body and install the cover. Do not overtighten the screws.