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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Rebore
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<blockquote data-quote="timetraveller" data-source="post: 7483" data-attributes="member: 456"><p>Yes, I worried about increasing the compression ratio if the base of the muff was reduced so I did a sum. The cylinder head capacity is 103.5cc on my heads and the swept volume is 499cc. Total is 602.5cc. [As an aside if you had a flat topped piston which did not protrude above the top of the liner then one would have a compression ratio of 602.5/103.5 = 5.8 : 1 (there's tractable isn't it?)] To calculate how much volume is contained in one mm of cylinder take a radius of the bore as 4.2cm, square it and multiply by PI and then divide by 10 (1 mm = 0.1cm) I make it that each mm of stroke contains 5.541 cc. Suppose we machine five thou off the base of the muff. Five thou is about one eighth of a mm and so the swept volume of a five thou slice is about 0.69cc. In addition one is not taking a five thou cut off the whole of the base but only of that part which is high so perhaps about half that figure is what will change. Feel free to check the sums and if they are wrong I will go and stand in the corner. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool :cool:" loading="lazy" data-shortname=":cool:" /></p></blockquote><p></p>
[QUOTE="timetraveller, post: 7483, member: 456"] Yes, I worried about increasing the compression ratio if the base of the muff was reduced so I did a sum. The cylinder head capacity is 103.5cc on my heads and the swept volume is 499cc. Total is 602.5cc. [As an aside if you had a flat topped piston which did not protrude above the top of the liner then one would have a compression ratio of 602.5/103.5 = 5.8 : 1 (there's tractable isn't it?)] To calculate how much volume is contained in one mm of cylinder take a radius of the bore as 4.2cm, square it and multiply by PI and then divide by 10 (1 mm = 0.1cm) I make it that each mm of stroke contains 5.541 cc. Suppose we machine five thou off the base of the muff. Five thou is about one eighth of a mm and so the swept volume of a five thou slice is about 0.69cc. In addition one is not taking a five thou cut off the whole of the base but only of that part which is high so perhaps about half that figure is what will change. Feel free to check the sums and if they are wrong I will go and stand in the corner. :cool: [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Rebore
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