Head nut 'O' rings.

[imago]

Many will know this I'm sure, but for those who don't ....

The oil leak from the front of the head on the GSX engines is fairly common, and is often mis-diagnosed as a head gasket leaking. It's rarely the head gasket leaking, 9 times out of 10 it's one of a pair of 'O' rings.

Cam cover off and at the front of the head there's a tube nut either side of the cam chain tunnel.

Remove the nuts and you'll see an 'O' ring on each. The nuts should be bone dry below the 'O' ring as it's there to stop the oil leaking out of the cam chest. These are wet with oil as you can see.

Replace the 'O' rings and put a smear of rubber grease on them to stop the 'O' ring binding on the tube in the head.

In the 1st photo of a spare head you can see that the contact face of the tube nut (below the 'O' ring) is open to air. 2nd photo of the one on the bike shows where the oil drips from, leading to it being mistaken for a head gasket leak.

Torque the head nuts down and button it back up. 

Edited May 22, 2023 by imago