Rebuilding a Carburetor

This will be quite a long post, to see it all, click “Continue reading” below. A while back I promised that we would upload a walkthrough on rebuilding the carburetors, here it is! This is a rebuild of the AS1/AS2 version of the carburetors, but the AS3 and most other versions are similar. To view a larger version of any picture, click on it.

Carburetor Rebuild 01
This assumes that you’ve already disassembled your carburetor and that you have all the required parts, either new or used. The tiny openings in the nozzles tend to get clogged over time, I would really recommend that you get a restoration kit that contains new nozzles and gaskets in order to get your bike running smoothly.
In order to make things easier to see, we’ve laid out all the parts here. Begin by assembling the nozzles in the upper part of the carburetor housing in the steps shown below.

Carburetor Rebuild 03
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Carburetor Rebuild 12
Now that the pilot jet, main nozzle, main jet and the valve seat assembly is in place, it is time to get the float in place. Make sure that the float rests in the proper place when it is attached, if not you can bend the tiny piece of metal that rests on the valve seat to get it to the right position.
Carburetor Rebuild 13
Carburetor Rebuild 15
Once the float is in place, it is time to attach the lower part of the carburetor housing. Remember to put the gasket in place first, it only fits one way round to it shouldn’t cause any trouble. It is important that you’ve removed any traces of the old gasket so you get a good seal. Repeat for both carburetors. As standard, there’s a small clip that attaches with the screws holding the lower carburetor housing used to hold the air vent pipe in place. If you have it that is great, your bike is one step close to original condition, if not: don’t worry! You can fabricate something that has the same purpose easily.
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Next, it is time to attach the air adjustment screw and the throttle screw.
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Now the time has come to assemble the choke. The only difference between the two carburetors with regards to the choke is that the right one is controlled by the rod attached to the tiny handle on the left one.
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Now you’re almost done! The main part of the carburetor is assembled. The next step is attaching them to the cylinders and coupling together the choke. Be careful not to overtighten the screws when attaching them to the cylinders: the aluminium is quite brittle and has a tendency to break if you overtighten them, if that happens you’ll have to go looking for new carburetors.
Carburetor Rebuild 51
Carburetor Rebuild 52

There are still a few things left to do. First, the throttle has to link up to the carburetors. We haven’t shown that in this update but I’ll just go over a few things: first of all, the cut out crescent on the throttle valve has to be facing the opening towards the air filters, away from the cylinders.

You also need to adjust the fuel and air mixture. A good starting location is turning the adjustment screws all the way in and then 1.5 rotations out. Again, adjust as necessary.

In order to set up the throttle, first make sure the throttle valve is at the very bottom of the cylinder by lowering the adjustment screw. Then adjust it on idle so it runs evenly. We will show all the setup and adjustments in a video, once the weather allows for us to bring a motorcycle outside. Once the video is online, I’ll add a link to this update!


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4 Responses to Rebuilding a Carburetor

  1. gudang klasik 2013/04/20 at 09:58 #

    thanks 4 shared ^ ^

  2. Martin Broodbank 2014/04/08 at 23:23 #

    Fantastic website. Makes my rebuild easier. Where can I get a rear grab handle from? Tried lots of places with no luck.

    • Joacim Larsen 2014/04/09 at 20:42 #

      I’ve sent you an email 🙂

  3. Mike Colquhoun 2019/04/03 at 17:35 #

    The one thing that has not been mentioned at all is the Bakelite inserts where the carburettors bolt on to the barrels. Are these available? I don’t even see these mentioned in the parts manual.

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