Also check the 7v regulator and all grounds as it also feeds the Oil sensor,
Err, not really. The 7 reg is just for bikes with 7V gauges
the oil light circuit is quite simple
At ignition on
power goes to one side of bulb then on to the pressure switch for a ground.
If the engine is not running or you have no pressure,
the spring loaded contacts are closed
and the circuit is complete so the bulb lights.
When motor runs, the pressure builds and lifts the contacts apart
this breaks the circuit so the light goes out.
When we get the oil light on unexpectedly, we all hope its the sender but
they are generally robust usually its an indication something else.
As Shep says, at 23 thou you wouldnt expect major bearings to go south
unless some PO has been caning the arse off it and/or neglecting things
Sheps strainer suggestion is worth try as any restrictions here could
obstruct the supply
hope its something simple cheap and easy to fix !!