Small Engines (Lawn Mowers, etc.): Kawasaki, loose bolt, silly putty

Question
I have a John Deere JX75 walk behind mower.  The engine is the Kawasaki with pressure lubrication.  The valve cover was leaking after the warranty period expired.  I was able to tighten the loose bolt.  But soon after it was loose again.  It would not tighten.  I left it and kept checking the oil for a couple years.  Then I had to remove the valve cover to find the problem.  Removing the bolt brought out lots of aluminum shavings.  Not good.  The threads were stripped out.  Not from overtightening by me.  As it would not tighten so I stopped the first time.  Took it to the place of purchase and they could not fix it.  So I tried a thread repair kit.  Fill the hole with silly putty and put the bolt in.  Let it harden over night and it held for 3 years.  Now its coming out again with more oil leakage.
So my question is can I heli coil the bolt hole for the valve cover?
It is the lower left.

Thanks,

Answer
If there is enough material, that is the hole is large enough to accept a heli coil you can try that.  I have an a valve cover which I installed a heli coil but it continued leaking a few drops of oil.  Much less than it was leaking but never the less it still dripped periodically.

Is the hole that is stripped in head or engine block?  If it is in the head it may be possible to find a used head on E-bay.
Let me know if this helps.
Eric