I'm putting together a 50 with a 55 (Huztl) top end. I turned the base down so that with a gasket I would be at 0.020" squish.
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I did some mild port work, mostly widening out the intake and exhaust, didn't change any timing numbers, and I also opened up the muffler with 3/4" tube, turned the baffle plate into swiss cheese and welded the original louvers shut.
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^ The intake
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^The muffler.
I figured this would be a good saw to try my hand on port modification as the parts are dirt cheap. It definitely needs the decompression valve, and I plan on advancing the timing slightly, probably 1/3 of a keyway.