I just took my ‘73 SC for a good run a few weeks ago running it in with a new set of piston rings. It went really well but when leaving the track and riding back off the track the engine keeps hunting up and down at low RPM. It is most noticeable when the engine idles in neutral and only when hot. I have fitted new engine seals not long ago. First time it has done this. Hope someone can help me out. 

Wonder if it's got a blockage in the pilot jet--or partial blockage & can't make its mind up as to idle or grab some air & rev a bit. Not choke lever holding choke piston hovering--that'd go rich unless choke jet restricted. All wild guessing. Air leak around the base gasket [sucked in or blown out]. Reed block gasket etc. SC's don't like going lean, or not up in the revs at least.