When I pulled the head off the F2 to sort out the oil leak I found a few underlying issues that may have contributed.
The 16 nuts that hold the head down, some of the threads were starting to strip on the nuts
2 pulled threads in the head and 1 on the barrel.
Cam tower wasn't able to be torqued down to spec (pulled thread) allowing oil get underneath and through the penny washer.
A side issue, #3 combustion area was black unlike the others. Valve guide seal was leaking letting oil down the valve and getting burned. No noticeable smoke, spark plug had the black glazed oil burning look. Cause - the valve had a burr on it so when the seal was put on it nicked the seal causing it to leak. Fixed that up and also replaced the exhaust one as well so there were both new.
It just goes to show that you don't always know what is the cause of an oil leak until you pull it down. Then you may find other problems. I hope this has it sorted once and for all.
A separate issue was my spare engine. Clutch slipping in 3,4,5th gears under load. Took out clutch, cleaned up plates and check tolerance, put back in adjusted, 4 rides later same thing. Found out that the clutch springs were 3.6mm out. Put some new springs in an all working well.
I hope this may help out some others
