Low mileage, low top speed
My Rebel 2005 has sooty spark-plugs, low mileage (60mpg), boggy acceleration, and low top speed (57mph).
The first problem (apparently) was stripped threads on the choke SE nut. I replaced that, but problems continued.
I cleaned the carburetor three times, and the last time with an ultrasound cleaner, and jets look very clean.
Suspecting the new air filter was blocking air flow, I rode 20 miles at 50mph without the filter, but still the same problems. The plugs were only slightly less sooty.
Honda Rebel 2005; Yamaha TX500 (prior)