Why not use
a compression tester hose and unplug the fuel injector associated
with the cylinder you are using ?

I'm sorry, I guess I really didn't make myself real clear! What I was
referring to was an air compressor that was for things like roadside
service, painting etc. Not really something that the average motorist would
use for himself (like for pumping up a spare on the side of the road etc.)
This was a conversion for a permanant air compressor. I was supposed to run
a constant 90psi. when using an old aircooled 1600cc engine and one side
Cyl's. 1&2 were the power source and Cyl's 3&4 had a "compressor head"
installed on them if I remember correctly. So, I would think that the fellow
that replied from Australia was correct in reporting that he saw one for
sale for about 1200 USD. The reason I remember it is that I was thinking
about building one when I was doing commercial painting as this compressor
would run three or four spray guns at the same time for painting roof
decking! We would have mounted it on a dolly and just wheeled it around
inside the buildings. I could go check in the basement as I do still have a
lot of "old " magazines, dating back to 1964, so I may still have and
article ! Tom