Hole In Cylinder

[PEB]

I am not sure how I missed it doing a top end. But last night when installing new orings on the head I noticed a small app 1/16in hole right above the power valve. The rest of the cylinder looks perfect. Any idesa what the hole is for? I had a clogged pilot jet and the bike ran lean for the better part of a day. Is it possible that I created that little hole somehow? My thinking is that the previous owner had it drilled but how i missed it the last time I had the head off is beyond me. Any ideas what it might be for?

 

[GMP]

That is a compression release hole for starting. At kick speed, enough air is bled off to allow eaiser starting. At running speed, its too small to have any effect. This has also been on KTM 300s and bigger 2 strokes for years.