I am using the oil pump to the right setting and it is definitely working. The spark plug, new from the beginning of the running-in process looks just about perfect. If anything it looks slightly rich, but not too rich.
I haven't been to the crank seals yet. Anything a noob like me can look for? I guess I'm going through a process of elimination and I was kind of hoping it would end at this top-end rebuild :) It's an old thing so I'm fearing the worst.
A while back before I cleaned the cap I needed to empty the tank and the flow would be fine for a while and reduce to a trickle/nothing, then if i opened the cap it would start again. On the basis of what I have read this lead me to confirm the venting/flow issue.
It'll be cooler when it stresses me a tiny bit less :)