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Old 06-05-2014, 07:28 AM
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Davezilla Davezilla is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: Happy times china girl books etc

There is a formula for determining the ring gap somewhere, maybe in Gordon Jennings' 2 stroke tuner's guide... usually the ring gaps on these are plenty wide enough that they don't need to be adjusted.
Port timing and ignition timing on these things is all over the place as well and you can have 2 engines side by side that are totally different but you can look up port timings in here and in other places to get an idea what works and what doesn't... or just ask, I'll answer if I see the question instead of sending you on a search and so will most of us.

My port durations are a little longer than I originally wanted because I used my old jug on my new bottom end but it still makes good low end power and the high rpm power is really strong, but if I remember right, mine are 126 for the intake duration, 132 for the transfers, and 168 for the exhaust. I'd normally run closer to 120, 125, 150 for my ports but since I had to raise my jug by putting a 1mm spacer under it to keep the piston from coming out the top, but the port durations came out about 12 degrees higher than I'd normally run on a piston port setup... It ran good when testing so I kept it the way it is and it's most likely the high compression and 44 tooth sprocket that lets me get away with those timing numbers, I wouldn't recommend these timings to a new builder but they are working...
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