I think you can do this just by removing the carburetor, fuel tank and air filter all in one piece, Stuart, though I haven't done it. There are just three nuts/screws to remove: the two holding the carburetor to the cylinder's inlet port, and the one holding the bottom of the fuel tank. See the red circles on these two diagrams from the parts list:
[Linked Image]
[Linked Image]

The speed control cable from the handlebars will still be attached to the fuel tank, but I think there will be enough slack in the cable to allow you to put the whole assembly to one side while you access the valve cover.

Since I haven't actually done this, I hope Joe Carroll or someone else will chime in and confirm it can be done this way.