Topic: CB500/500 sealing pucks, rubber nickels, whatever.

[DavePhipps]

Annoying little things that don't come in most aftermarket gasket kits. They fit in the top of the head and seal those six holes
My question is what exactly are they sealing? What happens if they leak?
It seems strange to seal these holes when right next to them if the cam chain opening which goes all the way through the engine.
Please enlighten this curios mind. 

[flybox1]

You've got 6 bolts (not studs) helping seal the head to the cylinder. 
On the 750, these bolts are between the cylinders, and to not interfere with the cam towers and valve train, they are recessed into the deck of the head.  Once in place, the hole the bolts are recessed into needs to be sealed.  The puck fits in the recess, and is pressured in place by the cam tower.

This is a 750 head, but the holes where the pucks go are access holes to these 6 bolts.  Thru the fins in the front and back you can see these bolts.  The pucks seal out the outside world and keep oil where it should be....

Please nevermind the red arrows.