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My '76 528 with dual Zenith carbs is bucking one time after every turn you make with it. It feels like it is out of fuel for 1 second and than runs fine again.

I checked the ignition timing but it was at factory setting
I checked all other ignition components and they are in good shape.
I replaced all vacuum lines and "wired" all lines like they should be (they where al hooked up at wrong places)
I replaced all fuel lines

Anyone with suggestions? Accelaration pump? float level?

When you look in to the venturi at the acceleration pump nozzles, it there any fuel coming out when you accelerate? (try with the engine stopped). They do get blocked.

I'm not sure this applies, but, my '02 has a Weber 32/36 and all I have to do
is remove the gas jets with a screwdriver & blow out the blockage,
screw 'em back in & clean the air filter when I got tired of doin' it.
I luv Weber carbs.!
Are they available for your application?
Once they're adjusted, there's no need to adjust again either. At least for me.

Cleaning out the zeniths is a bit more complicated - but I never found the jets blocked. I did have some trouble with the acceleration enrichment nozzles, they are curbed, and the orifice is quite small, so perfect for catching any dirt. The good part is that you can take them out without having to disassemble anything. Just be careful not to drop them in to the carburetor, and take care to put them back in the right position, the jet has to point in a certain direction.

@Falkenberg: Do I have to take the top part of the carburator of to get to them?

I have an ultrasonic cleaner so maybe I should disamble the carbs and clean them both?

I checked the fuel spray out of the acceleration nozzles and the rear carb one was a constant spray but the front one was not at all.

Looks like im going to take the carbs off and clean them in my ultrasonic cleaner.

Prepare yourself with patience.

I would not take them apart or out of the car unless really necessary. They are difficult to get air tight again at the lower layers where the spacer is. They might warp, there are no gaskets between certain stages, etc.

You might try to take of the top 2 layers, that will give you access to all the jets, clean out the float bowl, and you can blow through the channels on the parts remaining on the car with air pressure. There is a fuel filter where the fuel is fed in to the carb, clean that out as well. Check all diaphragms.

Remember, there is a hidden screw under the bolt holding the air filter.
Be careful of sticky gaskets, they break. I never even had the originals, but I heard that you might try to tap the pieces with a screwdriver to get the gaskets unstuck.

If I remember correctly, you can remove the acceleration nozzles without taking anything else apart. They are pressed in the carburetor body and come loose with little effort. You can take them out with a small set of pliers, or large tweezers. Just don't drop them in the intake

Falkenberg wrote:Prepare yourself with patience.

I would not take them apart or out of the car unless really necessary. They are difficult to get air tight again at the lower layers where the spacer is. They might warp, there are no gaskets between certain stages, etc.

You might try to take of the top 2 layers, that will give you access to all the jets, clean out the float bowl, and you can blow through the channels on the parts remaining on the car with air pressure. There is a fuel filter where the fuel is fed in to the carb, clean that out as well. Check all diaphragms.

Remember, there is a hidden screw under the bolt holding the air filter.
Be careful of sticky gaskets, they break. I never even had the originals, but I heard that you might try to tap the pieces with a screwdriver to get the gaskets unstuck.

If I remember correctly, you can remove the acceleration nozzles without taking anything else apart. They are pressed in the carburetor body and come loose with little effort. You can take them out with a small set of pliers, or large tweezers. Just don't drop them in the intake

Well put. I had those carbs on an E3 and they were the most disagreeable I have ever had. And I got to be an expert at removing the top of the carb, in place, and a few jets and cleaning out both the passages and jets with a quick shot of aerosol carb cleaner. Seemed like it was almost a weekly process.

My problems usually related to a bad idle, not bucking per say, although that was always a problem in parking lots when it was off/on, but just barely.

When I first got my 528 - I had the same issue that Falkenberg solved with his advice.

Pulled the accelerator pump nozzles, cleaned, replaced and the car ran perfect.

Later the carbs developed air leaks and became undriveable. Replaced them with weber 32/36 and haven't looked back

Bizz; that's just what I was hinting at without saying it!
The Weber reputation is that they don't offer many problems at all.
Although I've heard the side draft carbs may be trickier than the downdraft carbs?
Glad you chimed in. I'm looking for more opinions on this.

Today I took the acceleration pump nozzles out and guess what! One of them was bend so it was blocked! I've put vacuum on the nozzle and it was still a bit open but not enough to function good.

I also dropped the nozzle of the second, rear carb so I took both off and disambled them to clean them in my ultrasonic cleaner. All jets and nozzles where pretty dirty because you could see them getting cleaner when in the ultrasonic cleaner.

I've ordered 2 rebuild sets in Germany but I also need a new acceleration pump nozzle. Any suggestions where to get one?

Where did you get the rebuild parts? I'm getting closer to the moment that I will have to fix them as well.
I thought I'd be getting them from here: www.ruddies-berlin.de/
The nozzle - I don't know. Perhaps you can contact the site I've found, they seem to have some parts. If not, try to find a spare carburettor from ebay or similar.

I bought them from Ebay.de. They where 45 euro a set.

I also found a acceleration nozzle local! Brové Classics in Leek Holland!

Jelmer; did you find any Weber Carbs to fit your car & if so, how much?

No, I cleaned the Zeniths and ordered a gasket set which also includes o-rings, crush washers and diaphragms. It also includes thin gaskets to go between the bakelite spacer to prevent leaks.