Cylinder Mods on 1995 KX-80

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Jul 30, 2001
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#1
I bought a used KX80 for my son. It sounded like it had a little piston slap so I decided to do a top end. I had found a brand new cylinder (NOS) for dirt cheap and decided to put a new cylinder on when I did the top end. When comparing the cylinders, the cylinder that was on the bike had some obvious porting done which included a sort of mushroom shaped cut out on the top portion of the intake port. The cut out elongates the intake port and is machined about .050 to .060" deep into cylinder wall.
Could any one tell me what this type of modification does for this bike? This motor is pre-exhaust valve.