Post Generic clutch cleaning advise.
As many of you have noticed, I advocate cleaning the clutches quite often, rather than messing with carbs as the solution to a low speed/start off or acceleration bog problem.
Over time belt dust and oil mist combine to form a grime that will cause the clutches to stick/bind making it feel as if the engine has no power due to trying to pull as if in a high gear. Some have even mentioned a "clunk" or "pop" when coming to a stop. This is due to the clutch sheave hanging up and then snapping back to the idle position.
When cleaning clutches, do both the primary (on the engine) and the secondary (driven) units.
Start by removing the belt and inspecting it for wear. (normal or uneven)
Use an air compressor and blow out the inside of both units. (do not breath this dust in, it's not good for the lungs)
Then I use spray brake cleaner (some suggest warm water only, your choice) and flush them out. blow out with air and check the action, repeat steps as necessary. While you are in there, inspect for any unusual wear to the weight arm bushings, the rollers, and the center bushing. Replace as necessary.
After cleaning, ripe down the sheave faces with a dry cloth. Do not use any oil or grease on the clutch units. If you want to lube them, use a dry lube designed for this purpose, either in an aerosol can or loose powdered graphite.
This is what I use on mine; http://snow.parts-unlimited.com/4/55/5401885
Reinstall belt and have a blast with your new performing clutches.