Oil leak from exhaust

My 1982 1000 LTD is leaking oil. It appears at the joint between the exhaust header and the pipe that leads to the muffler. It appears to be leaking down the pipe from the cylinder head. I just had the head gasket replaced along with some other work. Could someone give me a possible diagnosis? Thanks.

Cable driven tach? These have a rubber seal and "O" ring that gets hard and leaks. Go to www.z1enterprises.com and order new seals for your bike.

Should be an electric tach on that model, same as mine.
How long ago was the top resealed? Has it had a retensioning? Unless it leaked from the start, then this may take care of it. It's recommended after the first couple of heat cycles to to a re-torque of all the bolts.