I'm reasonably sure that it's the cam joints, I did the same thing on my 80 2 years ago and replaced the oe's with factory Honda joints which didn't help at all and maybe slightly worse. I bought a set from Ian Billingham at cbxbilly6@aol.com. They'll cost you about the same for the new pair as it did for each of the Honda OE's and you won't believe the difference. While you're in there you might think about phasing the cams to the crank per the procedure in the Tech Tip Chronicles it's really worth the time. Good Luck,
Just a shot in the dark, try to tighten up on the exhaust studs and also do a leak down on the cylinders on that side. Sometimes, a head gasket leak or a exhaust gasket leak will sound like a "tap, tap, tap". It would be loud until the engine heats up and everything expands it then quiets down. It can get noisy again when the engine is hot and cooling down.