I didn't file it down, just took the intake side of it and shaped it more of a scoop. Not by much anyways. Butit likely was a stupid move but so is polishing the counter on the crank. I wanna reshape the top of the intake opening on the crankshaft trap door but I figureiI would really toss it off balance removing that steel. :/ a guy once told me you'd never be able to completely balance a single cylinder engine.. I never tried..