Repairs like this does comes in batches at times or at least they do for me. Since I am working ATVs, last year I had three come in one week all with bad starters. At least I had stocked the starters a few weeks earlier due to a sell at my vendor. When I first started doing repairs for others I ordered starters for Briggs and it was nearly 5 yrs before I replaced one then last year I replaced 6 in one month. I been at this current business venture for 10 yrs now but I have been doing equipment repairs for 40 yrs so I know things comes in batches, go away for years, then one day it starts again. I had one very difficult repair that I made notes for and it was a good thing I did as another one show up 10 yrs later with the exact same problem.
As carburetor problems I might several with a month with the same problem. I just repair them as they come in and don't worry about it.
Norm the more you work on equipment the more you will see things like this as these things are mass produce so a borderline part maybe installed in several machines during production. For example the Lincoln welder/generator that I repaired last week. The customer had a starter solenoid (relay to me) to fail. He buys one locally and install it. He still had the same problem of no start so he called me in. I checked the new part and it was bad so he had to exchange it. Guess what the exchanged one was bad too. I ended up installing one I had.
