How much compression does it have? Are the reeds in good condition? Are the crank seals in good condition? Have you checked the plug and ignition for proper operation? What I'm getting at is there's a lot of things that will cause the symptoms you describe, not just the carb. If the carb is clean inside and the jets weren't plugged, it should be working good enough to get the bike at least running. With that old of a bike, I'd check the compression and reeds right off the bat. There's a good possiblity that it needs the top end done along with reeds.
Marc -