Have an 80's GSX550 - Can't figure out what the red screw here is for?

[Airhead-emmy]

I'm trying to rig together a make shift wiring harness (barebones style) to make sure engine / plugs are sparking - before I go ahead and rebuild the wiring harness, and spend time and elbow grease cleaning and repainting everything.

 

Looking through Haynes Manuel I cannot tell what the red screw is for? Anyone have any ideas? 

 

Thanks

[Blubber]

Oil pressure switch would be my first bet

[Airhead-emmy]

Yep, put that into Eblag and can tell from the picture you are correct - thank you!