<-=- Club Bevel Heaven -=->

I've tried most things in an attempt to fix this - multiple gaskets, liquid gasket, wet & dry on a surface plate. The leak continues, only a few drops overnight but I'd like to fix it.

The photos below are after a run on the bike, one with a UV torch.




Is this a porous casting? What should I do about it?

Have you tried swapping out one or more of the other covers to see if that effects your leak? You didn't mention this. It could have a breech from debris hitting it from the front tire. It does take a beating from the front tire throwing up debris.
If it is a porous cover one of the others might cure it and putting this cover on top might also cure the leak because oil would not be sitting in it.

you say you dressed the flat on the cover - did you do the same on the head? If not, do so. Using a paper gasket yes? If using a new alloy type those have a more difficult time sealing up due to the porosity of bevel drive castings. If all else fails, I have some good used rocker covers for sale.

https://store.bevelheaven.com/Engine-Re ... vel-Twins/

Long ago, not paying attention, On my front exhaust valve cover, I tightened one cover bolt fully and then installed the rest and tightened them. Shortly after, drip, drip, drip from the lower left corner. Inspection revealed a crack on the inside horizontally across and in line with the area the countersink ended for the cover bolt. Being cheap, I sanded the area around the crack and epoxied the inside of the cover. Then installed it on the Intake side. That was forty years ago!