For some strange reason I am getting oil in the air cleaner from the rubbr tube that comes up from the vaulve covers. Why is this happening and what can I do to stop or prevent this? Or can I just plug up the hole with an rubber plug?

 

A little oil is normal. You need the breather tube so plugging it isnt a good idea. I would change the breather filter inside the air cleaner and see it it helps, $3. If engough oil gets soaked into the breather eliment overtime it will spew out into the air cleaner.

 

You might also want to check the PCV valve and its tubing for obstructions. The oil is likely from excess crankcase pressure, caused by a failed PCV system or excessive blowby. Blowby can be from either worn rings, or overloading the engine before it is fully warmed.