Ok I've now got my engine back in the bike. Have reconnected the oil system, poured a couple of 100ml of oil down each cylinder head by the cam chains and poured the rest of 3lts into the tank. I was told that after about 30 secs of turning her over the oil light should go out. It hasn't She is flying over as there are no spark plugs fitted. Oil pressure switch is def connected and after probably 2 mins of turning over it's still on. Am a bit worried as to why she isn't building oil pressure. Is it possible there is a air lock? I removed the oil pressure switch and oil trickled out there. Can't see any coming out of the return into the oil tank though when shining a touch in there. I know I could removed the cams and use a syringe to force oil down the lines from the top end. That is a pain though. Suggestions anyone?

just as a side note and not that it matters I haven't connected the rad system yet, throttle bodies or exhaust system.

Edit:
Just been thinking about it and the oil coming out of the oil pressure switch hole wasn't blue like I'm using but rather yellow which I pushed down the oil lines under cams as I rebuilt. Also I didn't fill the main line leading from the tank to the engine. This I guess is a suck line and was not full of oil but rather air. I'm thinking I need to bleed that line maybe?

should have built up pressure after turning over so long
also if turning over very fast could be a head gasket problem
would explain both problem,s

Ive gotta say ive never heard of an oil light going out until an engine actually starts and its up to pressure? Maybe im wrong or maybe its just something ive never questioned or thought about?

If an engine has a starting problem, lets just say youve left both plug leads off so the engine only turns over but doesnt fire, the oil light will stay lit whilst the engine turns over and will continue to show until the engine fires up

In your original tear down, did you disassemble the oil pumps for a check of wear. If so, when putting them back together, a bit of grease in the works helps them to prime.

Klinck - I would not have thought that the starter motor would provide enough rpm to achieve 'minimum' oil pressure, ie tickover rpm, but one other thought, if I'm wrong, is that the oil pressure switch wiring may be being shorted out by the adjacent coolant hose clamp, ie the common problem, but I thought that only happens when hot.

Turn over rpm is not fast enough to create the head pressure required for the oil pressure switch.

However idle speed should sufficient, if not then something is wrong

I've had engines which I've turned off after 10 seconds because they sounded like a Ducati. Started, turned off again Etc. Then on third run
eventually go quiet as the oil starts getting through. Stressful but not fatal. I recall many years ago at the Chrysler engine factory they
used to fire up the car engines on gas and let them spin at red-line for about 30 seconds whereupon they'd go quiet.

Can't recall ever seeing an engine prime without running.

Thanks guys, you've helped set my mind at ease. It was just the top end that was rebuilt, the oil pump wasn't touched. The oil lines are different sizes so it would be impossible, even for a numpty like me to fit them the wrong way round. I'm going to put together the last bits and fire her up.

Fired he up today. Took about 6 seconds for the oil light to go out. I was getting very close to hitting the kill switch but all is good. Happy days

Just on a side note the oil light does now go out when turning over. I have an issue somewhere, its either a bad electrical connector or the fuel line connector. Been trying to start her again with no joy but the light does go off after about 3 secs of cranking.

Out this am changing the oil on my Tiger and I had this