97 zx6 oil

With the amazing efforts of Dave#3 we swapped the engine from my tracky and put it in the frame of my late 97zx6.
after getting it started (this is a whole other story) we noticed the oil light came on and stayed on.

The oil, filter and cooler were removed to facilitate the transplant of engine, and i filled it back up with 20w50, the specs for the bike is 10w40. (20w50 is cheaper and im doing this on a budget)

Would putting thicker oil in cause the oil light to come on and stay on?
oil pressure sensor has been tested and working, oil level is at the top line, when the engine is running oil level drops about half way down.
some nasty noises can be heard up the top of the motor when starting it, but eventually gets quieter.

I am thinking the oil is too heavy and taking too long to circulate, but thought id post up and get some other ideas.

Did you check if you had an air lock in the filter..
Loosen the filter and run the bike until oil bubbles out, when the airs gone tighten it up...

Yep, the Boss is most likely on the money mate. Unless the oil pump on the new motor is cactus!

Had exactly the same problem. Follow MadKaws advice and the light of doom wil quickly dissappear.

Thanks guys, will give it a go on the weekend. Asshole neighbours don't like me starting the bike past 7pm