Here's one for the trivia collection! My Kymco 100 started stumbling at moderate cruise speed (about 60-70kph). The rpm's would drop about 100rpm every 10 seconds or so. Really annoying! I went through everything, clutch, variator, carburetor, plug, coil, etc. Nothing! It doesn't have a computer for diagnostics, so I had to figure it out the old-fashioned way, replacing everything one by one until I found the villain. Well, guess what it was: it was the stator. It appears they get old like the rest of us and then then start stumbling! Anyway, I ordered a new one from the dealer in France (AZ Motors), and it arrived 10 days later, plus a flywheel removal tool from Amazon Prime) and after an hour's work it was installed and running like a new one!
Now here's the takeaway for other Kymco owners trying to order parts. My stator is identical to a Kawasaki KFX90. There's no Kymco/Kawasaki interchange for parts, and Kawasaki denies that their parts are the same as Kymco parts, even though the Kawasaki parts say "Kymco" on the part. This time I wasn't sure, so I had to actually order the part from France. Sure enough, it turned out to be the same as a Kawasaki stator! Now I have one more Kymco part that can be replaced by a Kawasaki part!