Meanwhile you might check this thread:
https://www.outdoorking-forum.com.au/forum/u...&Words=centrifugal&Search=true#Post18930

Qualcast is now one of the ATCO brands, and ATCO in turn is owned by Bosch. If necessary you can contact ATCO with questions. However that may not be necessary. Can you show us a picture of the belt and the pulleys it runs on? So far as clutches are concerned, at least a couple of British mowers have used a centrifugal clutch to (hopefully) stop the reel, or cylinder, when the engine is idling. Since your mower is one of those types, it does sound as if it has a centrifugal clutch on the reel. It should have a hand clutch on the rear roller, to control forward propulsion.