Engine Oil Leak spraying left side of bike

I solved this problem and wanted share it for other forum users benefit.

77 mk111 850 has got 26k miles and engine has not been apart from new as far as I can see. Everything was fine and then i noticed a coating of oil spray on the the front face of the battery cover, siilencer, top of primary case and carb fuel feed pipe. This only appeared after a run and I couldn't see anything in the driveway even after covering everything with talcum powder and revving it up. I became convinced I had a leaky head gasket but a compresssion test and general running were fine. I thought oil was leaking from the front of the head and being blown by the air rush on the move. When I was stripping down the engine I removed the inlet rocker cover and found the neoprene gasket had buckled and pulled inside on its vertical edge. This must have been leaving a small spray hole that under certain engine conditions ( overun maybe) was sending a occasional jet of oil out sideways which then got caught by the wind and coated the areas noted above. It was not a steady leak from the bottom edge which is more common and easier to see. I replaced the neoprene gaskets with the red silicon ones recommended on here from Rocky Point Cycle and hey presto the leak has gone. I really didn't want to disturb the head which has behaved itself for 35 years and am so pleased that this niggling fault has been cured. Hope this helps someone some time.

Yep sir those silly con gaskets are the cat's meow for re-useable rocker sealing. They do wear out after a decade or so I've found. Tend to break up under the clamp bolt area. I've extended my worn ones by putting the decayed area at tops and so far so good but for how long. Oil form fork leak can also fool ya by where it appears after a ride. Leaks out master cylinder that's wind blown away can cause break to fail completely one full use to nothing at all the next instant. Check brake fluid time to time to know for sure.