I had 2 different brands of weed whackers that had rotted fuel lines and primer bulbs. A quick trip to Home Depot found a repair kit with a complete snap-in primer bulb fuel lines and 2 bulb tops. Both my weed whackers used the snap-in bulbs and not the type that clamp under a metal ring. I wanted to get both machines running quickly, so I bought 2 repair kits.
small bench vise, alligator clips, solvent-based plastic glue, soldering iron, small flat screwdriver and something to tap the screwdriver with
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: The Old Bulbs Were Not Made to Be Rebuilt
They do not unscrew or have reusable latches. After dissassembling one I still could not tell how it was originally sealed.
The 2 spare bulb tips in the kits are different sizes. The smaller one is the typical Walbro size.
To dissassemble the old complete snap-in bulb, clamp it in a bench vise gently by the back end and put the small straight screwdriver tip and tap it gently while twisting. The top ring will pop off with the old bulb tip in it.
Remove the bulb tip and replace it
Step 2: Glue the Bulb Together
Using some good solvent glue reassemble to bulb and hold it together until the glue dries. I used alligator clips.
Step 3: Secure the Bulb With a Solder Iron
The is no glue I know of that I trust to glue plastic and can withstand continuous soaking in gasoline mixed with oil, so I used a solder iron tip to melt the ring to the base as a permanent seal. That makes future repairs more difficult, but a sealed fuel system if normally a requirement for a properly functioning tool. A bulb with a pinhole leak will still prime but the fuel system will not hold pressure and most 2-stroke engines need a little internal pressure to keep the fuel moving.