Joe, that sounds as if the centrifugal clutch is in the engine output shaft, so it starts and stops both the reel, and the drum drive upstream of the drum clutch? If that is correct, drum drive is only available when the engine is running fast enough to engage the reel (cutter).
So, is the reel spinning when you can't get it to propell itself? If the reel is not spinning, the drum drive will not work until you rev the engine up a bit more and make it spin. Then the drum drive should engage. If the reel stops when you try to engage the drum drive, the centrifugal clutch is not fully engaged and you need more engine speed. If the reel won't run even when you rev the engine, there is a problem with the centrifugal clutch that is in line with the engine's output shaft.If the reel is spinning but the drum doesn't drive, then you are having some kind of a problem with the drum clutch or its manual control on the handlebar.
To go further with this, we need to know the results of those tests.
