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.
Step 2: Where to Mount an Improvised Clutch Housing
This is the same graphic from the previous step. Note the four holes in #5 (starter housing shroud) that receive screws #8 (follow the dotted line running through #7). These were used to mount an improvised clutch housing.
Step 3: Clutch Housing Mounting Tabs
When I needed to make this repair, I was much involved at a construction site. Pictured is an electrical panel. Notice the gray knockouts between the breakers. I gathered four of these from scrap materials on the ground. I bent each into an "L" shape. See the next step.
Step 4: The "L" Tabs for Mounting the Improvised Housing
Although this is actually a photo of the finished project, it also illustrates the "L" shaped knockouts from a circuit breaker panel. I drilled holes in both ends of the "L" pieces and mounted them with screws on the starter housing. Then I measured the space between the ends of the "L" tabs.
Step 5: Wood Block
I chose a piece of 2 inch stock with a fairly dense grain pattern and cut it to fit the open space between the four steel "L" tabs.
Step 6: Drill a Hole for the Boom
The boom is the metal tube that runs between the engine and the line spool and its head. I drilled a hole through the center of the wood block so the hole's diameter was the same as the outside diameter of the boom.
Step 7: Saw the Block Into Two Halves
Cut the block into two halves as shown. Notice the small circle on one face. Drill a hole for a long wood screw. Drill a like hole in opposite corner. These screws will clamp the block around the end of the boom to provide a rigid structure.
Step 8: Finished
This is another photo showing the completed project. The other photo of the completed project was in Step 4. By viewing both photos you can see the location of the screws that hold the two halves tightly around the end of the boom, as well as the saw kerf cut through the block to make two halves.
In this photo you can also see how a hole was made to accommodate and fit the throttle cable.
I have used this weed trimmer for more than ten years since making this repair and it has been as good as factory new. While the clutch now runs in open air inside the steel "L" tabs, it would be near to impossible to acquire an injury from the spinning clutch. You might never need to make this repair, but what I did might provide an idea for you for something you will need to do.