ST1300 Overheating

[cdnemsguy]

Put red ST1300 for sale last week. Bought a newer blue one. Took red for ride yesterday. Of course it developed a problem.... Pissed at me for putting for sale sign on her!!
over heating. Fans both working. Spitting coolant. Gauge went to 5 bars many times. It has never gone past three bars before. Limped it home after many stops to let it cool. Tore it apart today. Rad full. I assume thermostat. Just removed thermostat. How do I know if if it is stuck closed. 1000,000 kms, never replaced thermostat before.
Is this stuck closed? Are there measurements for open and closed?

Closed is closed. Boil water, put in a mixing bowl and dump the t-stat in. If it doesnt open right away it is toast as long as the water is above 180F. Cant see from the photos but is the brass etched on the inner sleeve? Green corrosion there as well?

 

[Happy Rob]

This might be a silly question.... Does closed mean the spring is compressed or de compressed?? I assume spring open allows coolant to pass the thermostat, thus open???

 

[cdnemsguy]

Closed is the disc is seated and will not allow coolant to flow through. Open allows coolant through. From cool, put it in the hot water and the plate should open quickly.

 

[ST Gui]

Just look at it at room temperature. Drop in it water at full boil assuming your not at high elevation and pull it out after a minute. If it looks exactly the same as before you dropped it it's toast— and stuck closed.

 

[TerryS]

Here's one I cooked earlier (showing correct function), you can see the valve plate (just above the spring) has moved down from the upper sealing ring to create an opening for hot coolant to flow.