To Start a Honda CA77

[mason123h]

I am currently trying to fix up a 1964 Honda CA77 Dream and I am having trouble starting it. I have looked at the wiring diagrams and have found the yellow and red wire that goes to the starter switch. The bike does not have a starter switch on it but I have tried hooking the bike to a battery and after testing the yellow/red wire for juice I ground the wire [that is all that a switch does right?] on the engine block, but am rewarded with nothing but a small spark [shouldn't it try to turn over]. I have tried this with multiple batteries and on multiple key settings to no avail.
Where on the bike/wire harness should I look for problems that cause such results?

Any help would be appreciated, I am not an experienced mechanic:)

Thanks!