Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
We love a good air leak on here After your grilling you'll be able to withstand a full round of mastermind, specialised subject; unspecified air leaks within 1970s Honda 400 engine architecture. Thinking about it, I was trying to flip the problem to see where I got. Sooooooooo, if you had the throttle tickover adjustment set so it gave a high idle when hot ( as in it was properly being held there) then consider it's too rich on idle screw adjustment to give stable idle over a full heat range. To test that, you'd have to lean the idle jets off by half a turn which should speed up the tickover, then drop the tickover master screw back out to bring rpm back in range. Maybe this would give a more linear setup over a wider heat range.Then get it hot again to see what you've got.
Plenty of ideas there chaps but no way am using my Chanel No.5 for diagnostic purposes!!!. No diagnostics going out at the moment as away in Prague with 4 girlfriends, all Nurses, so will fettle more next week.