New Hondas are shipped over with no oil, they are filled when sold.
They may stand unsold for weeks or even months.

I don't think you damaged a bearing if the oil light was out.
The problem may have been there already, the magnetic plugs don't pick up all the bearing shell wearing parts as most are non magnetic.

Did you say it sounded like a top end noise, what did you do when you removed the cam cover.

Run it up again for a few minutes with new oil and listen closely to pin point the noise.
The oil feeds to number 1 crank first, so number 4 will fail first if oil supply is poor. [RHS of the bike]

That had occurred to me, but at the same time, the whole thing has had me considering every possible angle. I am pretty sure it was probably like that when I bought her, but the dirty carbs did not allow it to rev up enough for the noise to be apparent.

The light was out every time I started her. After the trouble started, I even removed the cam cover and checked she was getting oil to the head.

I figured after this that a magnetic sump plug was useless.

I removed the cam cover, used sealant to reseat the gasket in the groove and then replaced the cover. That was it.

I have already taken the engine out but when I used a screwdriver as a stethoscope it seemed like either #3 or possibly #1.

DoktorMandrake wrote:That had occurred to me, but at the same time, the whole thing has had me considering every possible angle. I am pretty sure it was probably like that when I bought her, but the dirty carbs did not allow it to rev up enough for the noise to be apparent.

The light was out every time I started her. After the trouble started, I even removed the cam cover and checked she was getting oil to the head.

I figured after this that a magnetic sump plug was useless.

I removed the cam cover, used sealant to reseat the gasket in the groove and then replaced the cover. That was it.

I have already taken the engine out but when I used a screwdriver as a stethoscope it seemed like either #3 or possibly #1.

There is no need to use sealent on the cam cover unless you remove the gasket from the cover part, theyn you only use a very very small amount to stick the gasket into the cover part by the half moon shaped rubber pieces.

Ive seen a few where people ahve used sealer on the rocker box and its leaked into the head blocking up the small oil channels and destroying cams / rocker arms.

Not saying this is your issue but its something to be careful of.

That noise your having sounds separate from the engien RPM. coudl be anythign from exhaust maiflods, front / rear to start clutch bolts loose causign a rattle,

does it make the noise with the clutch pulled in? You could have a rattle clutch.

DoktorMandrake wrote:I have already taken the engine out but when I used a screwdriver as a stethoscope it seemed like either #3 or possibly #1.

The engine's already been removed from frame so re-testing's not really an option

Are you planning to repair the engine or replace it and strip/sell the original for parts?