??? on my gsr with a b16 head

 

Inside the thermostat housing

https://honda-tech.com/zerothread?id=1424191

 

follow the bottom radiator hose 2 the back of the motor

 

I'd suggest picking up an inexpensive Haynes or Chilton manual at your local auto parts store if you plan to check or change your thermostat. It will walk you through everything, and will also be helpful for any other work you do in the future.