You are probably well aware of this, but I wasn’t sure from your posting: the decompression lever on the handlebar had a dual function. The first half of its movement lifted the decompression bar on the front of the engine, the second half of its movement activated an ignition cutout. The handlebar lever had a sprung pin which, when the lever was fully pulled in, contacted a pin through the handlebar thus cutting the magneto. I have attached some photos…….
Apologies if you were already in the know on this point!