Featured One More 1977 Bonny Rebuild

Found an arty whatsit on photoshop so thought I'd stash the picture here for posperity...porputary....postuariry....postoperation...post sumthin......while it's still clean and before I start getting to it again with a spanner. Those zorsts will have to change, too skinny back tyre, and I don't like the muffler things, the seat is too big, I think I'd like a trackmaster tank.....

 

Cause of the lockdown this has been sitting in the garage looking pretty. (I gotta say that I've been enjoying the lockdown and will pretend that I haven't had the vaccine so I can stay in for a lot longer and not accept any visitors. I'll answer the door from the upstairs window as usual).
Anyway, the sun came out for a bit more than 10 minutes so I zoomed around to the dual carriageway and bombed up that for a couple of miles. Just as a sort of shake down.
Well, a couple of nuts loosened off that I hadn't tightened properly (the rear lights/number plate and the clutch lever pivot) and a couple of leaks sprang where they shouldn't be springing. The back brake needs sorting (although I did put on a new master cylinder) but it's the one with the calliper on the bottom of the disc so perhaps air. The PO had put the new thinner seat on, which is quite nice, but I assume came from a country over in the East. So the brackets broke and I'm not that bloody fat. They look pretty rough so I'll make some new stainless ones.
A bit of fettling to do then. Another reason or three to lock myself away in the garage then. Living the dream, living the dream

 

Put some more miles on the clock since rebuild and have solved a few issues. However, I like a tight motor so have been tracing the drips as they just get on my nerves. It pulls and rides well, I really like this one.
First was coming from the pressure relief valve, so will give me a chance to make sure the piston is operating ok, new large washer thingy and replace.
Second is a small one from the primary cover so will get back in there as I will probably get a new 7 plate clutch and pressure plate etc.
The third, and it's quite a big one, looks like it's coming from the head gasket ?? I originally thought it was the front rocker cover but it seems not. So I've sat in the sun and had a contemplate but have really just scratched my head about it.

 

The leak seems worse when the bike has had a run (it's only had two short 10 miler ones since rebuild) and the oil cascades from the bottom fin on the head down the barrel fins onto the the primary. It also covers the bottom fin on the head but that is probably just running to cover the hot head.
There's no evidence of the oil running from the rocker cover that I can see, so I thought it was the pushrod tube top leaking and somehow running round the zorst (cause I wonder about these things while not actually near the bike). Nope.
Only leaks while and after a run so maybe oil running down the front inner head bolt and escaping past the head gasket???
I'm obviously going to climb into it to check by removing head etc but I'm honestly not sure what I'm going to find, any ideas before I get the spanners out?
The arrow shows the head of the oil waterfall

It'll be a while before I get onto it as there's other stuff already in the way and I've loads to still do and spares to get for this one.

 

Took rockers and head off to check all. Was leaking from the back of the intake rocker cover which then dribbled over the head fins and onto the barrels. Looked bad when on side stand as it all then ran round the head fins and down the barrels on the left side.
Oil was present down the inside front left head bolt, and as I'm gonna be replacing the head (due to previous owner's erm.... rough handling while repairing), I've put in some dowty washers just to see how they cope.

Thankeee, over