The little "fork" attaches to one of the bolts that secures the cylinder head. The five minute run time most likely is due to fuel system clogs. I'd start there. It could also be due to other things (such as the coil, the condenser, the points, the spark plug, the plug wire). I'll see what I can do about coming up with a photo, but I don't have a digital camera (Miguel, I know you're still waiting on a pic). The decompression lever (the one on the cylinder head) is a piece of spring steel which is attached under the cylinder bolt. I've created a rough drawing of what the lever looks like and attached it.