I used to repeat the joke that “carburetor” is Italian for “don’t fuck with it.” Now I know it’s really just Italian for “removing and installing these from a motorcycle is the worst job I will ever have to do.” Removing hoses can be a pain sometimes, and squeezing and pushing the thick rubber boots holding the carbs in place between the immovable engine and barely-moveable airbox… Let’s just say that there is nearly always swearing involved, even on little single-cylinder bikes.

But removal and reinstallation isn’t what scares most people. It’s how they work that makes them run away.

The insides of a carburetor are complex, it’s true. In order to mix fuel with air in just the right ratio and quantities all the way from idle to full-throttle racing, a modern carburetor is a literal maze of tunnels cast and drilled into aluminum. You can map them out in many cases by tracing them from the outside and by visualizing a few imaginary lines. Still, there remains enough variety between carburetors to require real effort to decipher each one.

On the other hand, they all share a few basic circuits, regardless of what tricks they might use to work more smoothly or comply with emissions restrictions.

I had fun one day in class by bringing in the (easy-to-remove) carburetor from my 1950’s Cezeta 502, a thoroughly Czechoslovakian scooter. Looking at the outside, it’s almost entire different than Japanese carbs from the 70’s through today. With a bit of patience and a metric screwdriver, however, the workings become fairly plain. With any luck, now that it’s been cleaned out, it will do its job properly and I’ll be able to ride this scooter finally.

Meanwhile, I spent quite a while trying to get a friend’s Honda Helix’s carburetor tuned such that it would idle while cold, without stalling, but still idle at a normal speed with the engine warmed up. It’s a single carburetor, which should be the easiest to adjust. I will most likely be making a housecall at the end of summer, because I wasn’t happy with my results on the first and second go-arounds. Hopefully I’ll learn a few more things in the intervening weeks to help me find the answer. (One scooter shop I talked to said that they would just replace the entire carburetor — at $80/hour, this actually makes more sense than fooling with the thing for five hours, and it’s entirely possible the carburetor is worn out.)

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