just done a camchain replacement on an 8 valve k100lt.

flled up the fluids (new oil, BMW filter and antifreeze mix) , hit the button, all going well and good.

turned it off, left it a while, turned it back on again, and now the oil light is doing something strange.

with the ignition on the light is barely glowing. start the engine and it glows a bit brighter. rev the engine and it goes brighter.

bit odd IMO because if it was low oil pressure it should be bright at first and stay bright if the pressure was low, or if the system was running a bit low (as in not 100%) on pressure it should start bright and get dimmer instead of the reverse.

i realise these bikes have their idiosyncracies, so i thought i´d ask in case it was a known fault.

cheers guys!

Not heard of that, when you replaced the filter did the old rubber seal on the base of the old filter get left behind, I have heard of that happening on cars and because the filter is in the sump there would be no sign of the oil squirting out all over the floor so would go unnoticed. Check the old one still has the rubber ring on the base.

Given you were inside the fairing doing the anti-freeze change is there a chance you disturbed any of the electrical connectors (including the oil pressure warning light down by the pump, or any earth connections? and have you cleaned them all and treated them with DeoxIT?
Regards,
K-BIKE