This is a scanned photo of my weed trimmer. The centrifugal clutch inside the clutch housing (yellow square) came loose and chewed the plastic clutch housing to pieces so that the engine hung loosely from the throttle cable. I checked into getting a new clutch housing, but encountered only dead ends.
(The reason the clutch came loose was that I tried to open the machine so I could tighten up the starter cord. Doing that compromised the clutch's retainer. Although I tried to improvise something, it did not hold.)
Step 1: A better clutch retainer
This is an exploded drawing from the weed trimmer's manual. I added the colored items. The first step was to make certain the clutch bell (larger cylinder between the green and yellow boxes, right most of the three lines from #11) could not slide forward from the centrifugal weights assembly (#10) on the clutch bearing (smaller cylinder left of the green box) and the shaft connected to the engine (black cylinder portion in the green box). I drilled a hole (red circle) through the clutch bell assembly and just a little into the black shaft in the green box. I threaded the red hole for a set screw. I locked the setscrew in place with a tack weld. I filed the weld at the setscrew smooth so it does not rise above the surface of the clutch bell's shaft portion. If I ever need to remove the clutch, I will drill out the setscrew tack weld.