74 GT750. Pink. Had nto been started for a couple months. Electric starter turned over the engine 2-3 times, now the starter just spins when I hit the start button, but does not engage with the engine to turn it over.
Suggestions on where to start welcome.
Kevin
Everything Commeth
To He Who Waiteth
So Long As He Who Waiteth
Worketh Like Hell While He Waiteth
You may have to pull the left side engine cover to inspect the starter clutch. From what you're saying it sounds like the starter clutch has got a problem.
I don't know if the bike was changed back by accident to an older style clutch bearing and bushing in the past, but the early one piece starter clutch bushings failed from lubrication issues due to the design.
The bushing gets pitted and the needle bearing then collapses sending their parts into the starter clutch and seizes up the sprag rollers.
It was quickly updated to a two piece sleeve and bushing design long before 1974. Your 74 should not have this system but it might be in your bike if parts were changed from other engines during a past rebuild.
Pull the starter clutch and inspect the rollers and springs. They are sticking and not allowing the rollers to slide in and grab the shaft by the sound of things. Or maybe the key sheared. If that's the case the tacho won't work and neither will the water pump. And the points would be wrong too.
Had nto been started for a couple months. Electric starter turned over the engine 2-3 times, now the starter just spins when I hit the start button, but does not engage with the engine to turn it over. 
I'm out of town for the weekend, will check the above when I get back.