Any thoughts on this?
Two cylinders, same make and model bike, same part # cast into them, identical in all ways but one. The one in the first picture has a 3mm hole above the exhaust port and the second one doesn’t. I always assumed that hole was there to keep positive pressure on the power valve to keep it from fluttering, but why wouldn’t the second cylinder have the same hole? I have no reason that hole was put there by anyone other than the factory.
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