The Best Carburetor Option Yet?

Air intake view

Manifold side

Accelerator pump is cylindrical piece on left bottom

Electronic choke is in upper right hand section in this picture

It has an accelerator pump like the original equipment Pallas 22mm. It also has an electric choke, which means you don’t have to pump the gas to start it. It has a 46 mm intake opening for an air filter.  Don’t be embarrassed if none of these stats are familiar; not one of them is a standard Heinkel measurement.

You may also need to re-jet the carb, but I’ll talk about that at the end of the post.

Making a new throttle cable: The Oko carburetor has different ends than a Pallas. Not to fear, you can make your own cable quite easily. I used a Venhill U01-4-101-BK Universal Motorcycle Throttle Cable Kit – 5mm OD, made in the UK. Cost was $16.99 delivered to my house. The only trick is here is to determine the proper length of the inner cable. Loop the outer cable up and over the engine and then down into where the carb will sit. Then measure the distance from the top of the adjuster to one of the cable holding holes on the carb. That’s your distance.

Running a wire for the electric choke: The electric choke replaces pumping the throttle when you are starting the engine cold. The electric choke is temperature activated by an electric current that comes from the ignition circuit. The other end of the wire runs to ground. The easiest place to pick up the ignition circuit is where all of the black wires meet up under the dash, so you need to run a wire all the way back to the dash. I setup my carb with electrical disconnects so I could easily take it apart if necessary (and it has been necessary a few times).

Disconnects for electronic choke

You can see the black wire under the tube. It would be a tight fit in the tube but you could do it if you had time

Making airtight seals: The Heinkel carb intake manifold has a 28mm outside diameter. The new carb has a 30mm opening. There are two ways to bridge this gap- make a custom manifold adapter or find some off the shelf component. Luckily there is an off-the-shelf solution (sort of). I poked around my local motorcycle salvage yard and came up with a “spigot manifold”. The manifold solves the carb side of the problem. Here’s an example of one I purchased from Amazon that is an exact fit:

Perfectly sized spigot manifold

Installed on carb

The other end I solved using 3 o-rings slid over the end the Heinkel intake manifold. I used 1 1 1/8” inside diameter 1 3/8” OD O-rings, which are a common size in the US and cost 50 cents each. I assemble everything with screw clamps and got a great fit.

1 3/8″ OD O-rings – 3 required

Put one on the manifold

Put two more inside the spigot manifold

Installed – a really nice fit