Carburetor Parts Guessing Game
Some motorcyclists don't even want to know what's inside their carburetors, but that probably doesn't apply to you if you've clicked a link to visit this page!
For those of us who do care, wonder about, and consider the miniature wonderland inside our carburetors, the names of those parts often remain a mystery. Your chum calls it the jet-thingy, the shop manual calls it by a number, or a confusing series of abbreviations, just how is a rider to know what those wonderful little bits are called? Hopefully this game will help.
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The Objective
Match the name with the part! There are 8 carburetor parts listed below by name. There are 10 parts in the photos (some parts are represented by two photos for clarity) but of those parts, only eight of the parts actually go into a carburetor.
Guess which photos go with which part names, and guess the two 'red-herrings', the parts that do not belong, and are NOT carburetor parts.
Part Names
1. Carburetor O-ring
2. Carburetor Needle Jet
3. Carburetor Jet Needle
4. Choke plunger assembly
5. Choke gang pull bracket
6. Carburetor Float Needle
7. Carburetor Slide and Diaphragm
8. Carburetor Float
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The Parts
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In each photo below a purple arrow indicates the relevant part. Match the 8 part names above with the photos below, and identify the two parts that do not go in a carburetor.
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Functioning in essentially the same way that bulbous thing on a stick does inside your toilet tank, this part is usually filled with air, or constructed out of a foam-like material with many small air-pockets.
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The chemical engineering that goes into making plastics and rubber-like materials such as o-rings that can live in the harsh gasoline environment of a carburetor is amazing. I know the first carburetors were made before these materials were developed, but I don't know what they did in place of them.
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One of the many carburetor parts made out of multiple materials, this delicate little part is hung, or suspended, pivoting, from one of the other parts on the list, which itself also pivots.
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This stamped steel item, pictured to the left and below, seems to be made to connect 4 things, but what four things? Carbs? Chokes? Enrichers? Gauges? Or is this actually a part off my vacuum cleaner?
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Another one of those tricky little parts, made out of even more, even smaller parts, and different materials too. The body and the main shaft part are brass, the black material is partly a hard plastic resembling bakelite, and the spring looks more like steel.
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My very favorite carburetor part, these delicate aluminum spears, miniature knitting-needle-like parts, which on some carburetors have circlip grooves as a retention system, or multiple grooves making them adjustable. In the case of these four identical parts, they are held in place by a fixed head, and so are not adjustable.
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A view of this lovely part in it's home, centrally located inside the body of the carburetor, inside another part that travels up and down overtop of this part. In some ways this aluminum part is the heart of the carburetor, although some would dispute that analogy. Aren't carburetors complicated?
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These beautiful brass parts are very purpose built, with holes of an exactly measured size. Cleaning them must be done carefully, and the holes must be both clear and unaltered by the cleaning. Reaming these holes out to a larger size would dramatically effect the performance of these carbs, allowing more air through, leaning out the mixture and impairing mid-range performance.
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Well, it's pretty obvious this is an o-ring (unless it's a very over-toasted cheerio) but is it a carburetor o-ring, or maybe the o-ring from a maglight flashlight? After all, one o-ring is very much like another isn't it? Carburetor o-rings are made to withstand the harsh gasoline environment in which they live, and they are very specific and exact sizes, in Mikuni and Keihein carburetors, specific metric sizes.
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This intricate little stainless steel part has a pair of ridges at either end, which might be meant to create a groove to hold an o-ring or an indentation to fit a circlip or retaining ring.
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Most carburetors, for both two strokes and four strokes, have springs associated with them, some several kinds or sizes of spring. Is this a carburetor spring, or some other kind of spring? Looks a bit too familiar maybe?
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The Answers
When you're ready to review the correct answers below, you can scroll down the page to see each of these parts identified by their photos and a brief description of their functioning when assembled into complete carburetors.
If you really know your carb parts well, and you're just curious to see a photo of what these carburetors look like when they are all assembled, you can scroll down past the answers to see photos of the complete carburetors, both disassembled and in their assembled state.
Part Names
1. Carburetor O-ring
2. Carburetor Needle Jet
3. Carburetor Jet Needle
4. Choke plunger assembly
5. Choke gang pull bracket
6. Carburetor Float Needle
7. Carburetor Slide and Diaphragm
8. Carburetor Float
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Carburetor O-ring
This is a carburetor o-ring, made of a material suitable for the gasoline environment and in this case, equipped with a Kawasaki part number. Worth considerably more per gram than silver. Precious, precious carburetor o-rings. Cherish them for all they are worth, and wipe them carefully with oil before installing.
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Carburetor Needle Jet
This is a needle jet, to distinguish it from the pilot jet or the main jet, both of which, in these carburetors, are smaller than the needle jet, despite whatever images the name may conjure. The needle jet is responsible for controlling the mid-range power performance. The pilot jet is responsible for performance at idle speeds, and the main jet is really only responsible for wide open throttle applications. I imagine the main jets in these carburetors will be happy they get to go racing!
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Carburetor Jet Needle
The beautiful jet needle, a precise and elegant, jewellery like part and one which took me ages of delicate work to clean to the state you see here in the photo.
The jet needle goes inside the needle jet, and also inside the slide, like the very smallest egg-shaped doll inside the middle of a set of Russian nesting dolls.
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Choke plunger assembly
This small assembly of parts has a sliding, plunger action, and this little assembly, when connected via the gang pull bracket, allows one choke control to operate the choke function of four separate carburetors, through four of these plunger assemblies.
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Choke gang pull bracket
Attached to both the four choke plunger assemblies and to the choke cable, this bracket connects a single control to operate the four plunger assemblies, and so activate four separate choke controls on four carburetors.
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Carburetor Float Needle
This is the carburetor float needle, a stainless steel housing with a viton tip, and the tip is spring loaded on the inside so as not to jam. The needle acts as a plug to govern the flow of gasoline into the float bowl, controlled by the position of the float.
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Carburetor Slide and Diaphragm
This is the carburetor slide, which moves vertically with the jet needle inside it, and at the top of it, the diaphragm, a very delicate flexible rubber part bonded or affixed to the slide. The diaphragm creates a seal that allows vacuum pressure to suck the slide up according to engine load.
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Carburetor Float
This is the carburetor float, which acts in a very similar way to the float in your toilet tank, by using buoyancy as a way of judging fluid volume or level, and activating a control. In the case of a carburetor, via the float needle to control fuel flow, and in the case of your toilet tank, to control the water flow.
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Watch strap pin
This beautiful surgical grade stainless steel sprung pin is actually part of a watch strap, not part of a carburetor, although it's certainly a very trick little manufactured item, in this case it's one of the red herrings.
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Pen spring
This is a retractable pen spring, not a carburetor spring. While some carburetors have springs that closely resemble pen springs, the ZXR 250 carburetors pictured in this guessing game has springs that are all much larger than a pen spring. This is red-herring number two.
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More Carburetor Information
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These are the Kawasaki ZXR 250 carburetors pictured above, in their disassembled glory, showing all the wonderful bits and pieces it takes to mix gas with air successfully for combustion.
Cleaning all of these carburetor parts, assembling 'like new' carbs for your vintage racebike, is a very important step. One that, I confess, took me most of a year to accomplish. Although now I know much more than I did before about my carbs; I couldn't tell you the difference between a needle jet and a jet needle before!
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Here are the carburetors in their assembled state, with a view of the air-intake side and the butterfly valves. You can also see the choke gang pull bracket, but the little plungers themselves are tucked out of sight. Some of the springs appear in this photo too.
About a hundred parts, made out of at least a dozen different materials, all precisely assembled and working together, for the purpose of creating the perfect air-fuel mixture for internal combustion.
All hail the miraculous carburetor.
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