Rebuilding a Zenith Carburetor

Dear Dr. Motorhead,

I’m a bit of a do-it-yourselfer. I enjoy working on my old boats, both the woodworking and mechanical aspects. I enjoy your tips and advice. Most of the time I know what your answers are going to be, however, I have a problem. I am in need of rebuilding a carburetor. Although I have done this before, I have always been able to purchase a kit with all the gaskets. I have checked everywhere and no one has a set. I even called the folks at Zenith Carburetor – nothing to be found. Who do I turn to? You are the only one who seems to have all the answers to the many mysteries of our antique boating hobby. I turn to you and your wisdom for this great mystery. Where do I go and what do I do?
One (for the moment) without gas.

Dear Gasless one, In one respect, I’m sure your mother would be proud of you, but I’m not going to go there now. You don’t have a problem at all. In fact, after this lesson, you may never buy a carb kit again. Although you may not need help in taking things apart, I will include all the information for the rest of the readers.

The carburetor takes the gasoline, forces it through some little orifices (jets) which atomizes the fluid mixes. This atomized gas, with some air, gives you a mixture ready for ignition and the internal explosion. Today’s carbs can be quite complicated, however, the old ones are about as simple and basic as you are going to see. Here is what you do. First, go and buy yourself the following stuff:
> one roll of fiber gasket material,
> two cans of carburetor cleaner,
> one can of black spray paint,
> one gallon carburetor cleaner soaking solution.

What you are gong to do is take this thing apart, give it a good cleaning and put it back together. With new gaskets, you will soon learn how to make, and fiber washers you can buy at any hardware store with a good plumbing department you will be able to rebuild your carburetor.

1. Lay a clean towel on your work bench.
2. Split the carburetor in half and carefully pull the two pieces apart, being careful not to bang the float around.
3. Take out the hinge pin on the float and remove this and the brass needle.
4. With a screwdriver, remove the brass seat the needle sets into. There is a small brass tube screwed into the top section.
5. Remove this with a ¼ inch wrench. When you remove these brass parts, they will have a fiber washer on them. Sometimes this washer stays in the hole.
6. Carefully remove them and set all the washers to the side, for now. 7. Now take the lower piece and remove all the plugs and idle screws. Basically remove all the brass fittings (needles and seats), again making sure you get the fiber washers.
8. The high speed mixture adjustment (the big one on the back towards the bottom) has a small rubber “O” ring. Take this off and set it to the side as well. Now you should have a bunch of big and small pieces. If the brass pieces don’t come out easily, use your torch to get them loose. Be careful – they nick up easily and have very small holes in them you don’t want to damage.
9. Put all the metal pieces into your can of soaking solution EXCEPT THE MAIN NEEDLE YOU FIRST TOOK OUT WHEN YOU REMOVED THE FLOAT. This may have a rubber end on it and it won’t survive the soaking.
10. Let all this set overnight. If you have access to a hot tank, this is best, but the gallon can type works as well.

While you are letting this soak, go to your favorite hardware store and purchase new fiber washers from the plumbing department. Don’t forget the little “O” ring. If for some reason you can’t match up a fiber washer, don’t despair, you will make one later.

After everything has soaked overnight, pull it out and set it on your clean towel. Take each piece and squirt it with the carburetor cleaner. Give it a good bath. Wear glasses – this stuff flies everywhere. Squirt all the orifices and all the holes, making sure you blow out all the crud that may be in, on, or around all the pieces. If you own an air compressor, blow everything out with this as well.

Now you are ready to put it all back together. If you were unable to find the correct size fiber washer, here is how you make one.

I use a leather punch and punch a hole the correct size in the gasket material. Insert the fitting into the new hole and cut around the outside of the fitting with a razor blade. It’s as easy as that.

Submerse your float in water to make sure it doesn’t have any holes in it. No bubbles? Then you’re O.K. Before you put the two carburetor pieces together, you need to make a new gasket. Lay the bottom half on your bench – or better yet – set it in your vice. Lay the gasket material on top of the bottom half and with a small ballpeen hammer, tap around the edges. You will leave an indentation in the gasket. You can either cut this with a blade or continue tapping until you cut through the material. Using the round end of the hammer, you can tap any hole you need into the gasket. Once it is all back together, unscrew your high speed and low speed jets one and a quarter turns out. I prefer to paint the whole carburetor with the black paint, then, with a rag dipped in mineral spirits, wipe off the brass pieces before the paint has a chance to set up.

So, in true fashion, you asked how to find a gasket and I told you how to rebuild a carburetor. You can use this technique to make any gasket on your engine.

Dr. Motorhead