1974 honda cb 750 ignition/starting problem
 

Hello all,
Im having touble with running in general. I have been working on this bike, been in my uncles shed for 27 years! I've got new plugs and got it to turn over, but I've got no spark! Ive tested my coils and get 4.5 ohms of resistance? I turn it over with the plug touching grounded metal, but no spark. Although I am not familiar with points and condensers(before my time) I can't see anything disconnected or burnt. I've got a rebuild manual, and checked and re-checked all wriring. I'm stumpted!
thanks