The valve clearances will have absolutely no bearing on the oil pressure. If the engine has been run and oil is circulating I'd expect there to be a pool of oil when you removed the horizontal cylinder exhaust valve cover. In the past I had heard tales of oil pumps becoming airlocked resulting in no oil pressure but had never experienced this nor known anyone who had. However, Last November I drained the oil off my 907ie (same bottom end as 916) but left it over winter until March before filling it up with fresh oil. When I started the bike the oil light stayed on. WTF! The bike had been running perfectly before it was laid up. I removed the oil pressure switch wire and the light went out, if I grounded it the light came on. So it was definitely either a faulty switch no pressure. So I removed the oil pressure switch and used an oil can to squirt oil down the hole until it would take no more oil. I refitted the switch, fired up the bike, and the oil light went out immediately. It seems that over winter all the oil had drained from the pump and the pump, being a gear type, can't generate enough suction to lift the oil from the sump when it is full of air. By filling it up from the oil pressure switch the pump then had oil in it which enabled it to work correctly. This may not be relevant in your case but the oil pump must be primed with oil on a rebuilt engine or it will not pump.
Not had this problem on a bike engine but many years ago as an apprentice I rebuilt a mini engine which started up fine but would not build oil pressure at all, the answer was to prime the oil system and instant result with no further issues. Those rockers look seriously dry to me.
Thanks. Pulled the oil pipe off the Cooler and turned it over on the starter, and oil is being pumped. Also took the Feeds to vertical head off, and there is oil coming here also. However there was not yesterday.... So I think there may have been air in the pipes and taking the feed pipe of the cooler has released it. Will check later with gauge to see what oil pressure I get now. Hopefully this will have fixed the issue.... Cannot see it but would be great!!
It's quite common on the car rebuilds to pack the pump full of grease to prevent lack of oil suction in to the pump. Good idea priming the pump from the the oil pressure switch feed!.
