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Rebuilt

In mechanics training school in the early 1970s we students were indoctrinated into an understanding of the word "rebuilt" that meant a certain percentage of an assembly's parts were replaced. Something like a minimum of 10 percent. I believed this for a very long time. It is in fact why I avoided using the word "rebuilt" in the titles of all of my how-to booklets in the early years. But, it turned out to not be true. The Federal Trade Commission's Title 16 Code of Federal Regulations, Part 20, Sections 20.0 through 20.3, recently updated but essentially unchanged since its inception, enumerates very clearly the criteria for calling a system "rebuilt". It couldn't be simpler and it's what any concientious mechanic will do.

1. The part or assembly must be completely disassembled
2. The part or assembly must be thoroughly cleaned
3. All significantly worn parts must be replaced

The code allows serviceable used parts to be used in the rebuild, but it warns that mere cleaning, refinishing or making minor adjustments do not qualify as "rebuilding".

The reason this subject is important is because some people think motorcycle parts rebuilding, whether carburetors, engines or brakes, is essentially just cleaning them. The truth is carburetor rebuilding is nearly as labor-intensive as engine rebuilding. In fact it's almost all labor. Very little involves parts. In addition to ultrasonic cleaning and knowledgeable adjustment, carburetor rebuilding is separating parts the factory regards as permanently attached, thread repair, machining, welding, fabricating, straightening, broken screw extraction, polishing and blasting and electroplating, sourcing half-century old parts, identifying, evaluating, quantifying, repairing, preparing for racing, restoring to concours specification, adapting to other engines, reversing corrosion, correcting other people's mistakes, measuring, tuning, troubleshooting, functional testing, and quite a lot more.