101 1300 rebuild part #13: Weber 28/36 DCD

It was a tough decision, but after weeks of debating, test fitting, consulting experts and looking for patterns in tea leaves I decided to go with a Weber 28/36 DCD that I got from Conrad in exchange for some valuable emergency brake components as used on cars with the big Veloce gas tank. One local expert posited that a 1300 normale with this carb and ‘decent’ cams will out perform the stock Veloce set up of 1959. We shall see. In the interest of thoroughly documenting this rebuild I plan on running this thing on a dyno to dial the carb in and try out a few cam options I have. Anyone care to donate a little dyno time to a good cause? I’ll give you endless accolades in my write ups.

As always, the teaser picture is actually the near final product. This carb looks pretty good but required $130 in new parts from my local Weber parts dealer. With the phenolic insulator block taking up about 6mm you can see the mounting nuts don’t fully engage the studs. Oh well, this is not a suspension component.

At the start of the project I had my choice of two carbs. The condition of each was about the same but the one I chose didn’t have the studs installed at the top, which would have interfered with my air cleaner, and it had the correct linkage already installed.

Here it is freshly opened up. I decided to go with a new float as $29 is cheap insurance against being stranded in Honeydew California with a sunk float. There is some deposits in the carb that can be seen here, but overall I am pleased with the condition as a starting point.

The rebuild kit, another $29, came with a new needle valve which I installed. The float is adjusted by ‘hanging ‘ it from its fulcrum with the carb top perpendicular to gravity and bend the tab that pushes on the needle valve until there in 5mm of clearance between a tangency to the float body and the machined sealing face of the carb top. I measured 5mm with a metric allen wrench.

Here it is after all the venturis, jets and the like have been removed. I used some smelly aerosol carb cleaner and a new brass brush to clean it up. The cleaner ate through my gloves pretty fast so I was careful where I pointed it during spraying and wore my big safety glasses.

The four screws seen here hold the cold start actuator mechanism. I took it apart and cleaned it up, now it feels pretty good when I move the lever. Note the throttle linkage seen here and the position of the return spring.

Here I am putting it all together. With the new float and gasket it looks very good.

The Venturis just pop in and out, only requiring you to overcome the spring force of a detent. I can imagine how hard it would be to remove these on a gummed up crusty carb.

I believe this is a main jet and that is an emulsion tube laying next to it. I got a starting point for jet sizes from a posting on the 750 101 Yahoo group as seen below.

Weber 28/36 DCD jetting

Venturi 24/24

Aux Venturi 4.5/4.5

Emulsion tube F13/F13

Main Jet 130/130

Air corrector 210/150

Slow Run 50/-

Slow Run Air 175/-

Pump Jet 60/-

Pump Discharge 0/-

Float Level 5.0/-

I dont know how sensitive the above are but I am learning and will write about it as I discover it.

Here I am installing the Emulsion tubes and their associated jets.

First picture of it installed. I have a Solex top adapter that will work for the Air box I have.

This is another line item crossed off the list of things to do before this project is done. I don’t know if it is going to be perfect, but I think I’ve established a good starting point. I’d love to hear from you if you’ve put one of these Webers on a Giulietta and can provide component size information. Drop me a line at sprints @ giuliettas . com. Up next: more!
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