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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Compression ratio
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<blockquote data-quote="davidd" data-source="post: 54449" data-attributes="member: 1177"><p>Bill,</p><p></p><p>It is becoming clearer, but I am having difficulty focusing on the issue. The bike should kick start for you it seems to me, because you are using a decompression lever. If you are not using a decompression lever you need to use rollers of some sort (or bumping.) I know some electric starter owner who use the decompression lever with the electric starter, although I do not know whether this is an "approved" method. So, assuming there is nothing wrong with your starter, the only solution is to use a decompression lever to initiate starting. I say this because, and this is a guess, the compression ratio may be high, but I don't think it is wildly high.</p><p></p><p>You are talking about a mechanical compression ratio of 9:1. I don't know when your intake closes, but the corrected compression ratio is probably 8:1. If your combination of parts were to jack up the corrected ratio to 9:1, it would still run well on 92 octane pump gas. If the compression ratio were higher you would hear 'pinking.'</p><p></p><p>I think that attempting to measure the net volume in place is impraticable. The mechanical compression ratio is measured assuming the valves are closed. This is not what occurs. The corrected compression ratio, which starts the calculation when the intake valve closes can be done by formula, but it is always lower than the mechanical compression ratio. This leads me to think that there is something else going on.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 54449, member: 1177"] Bill, It is becoming clearer, but I am having difficulty focusing on the issue. The bike should kick start for you it seems to me, because you are using a decompression lever. If you are not using a decompression lever you need to use rollers of some sort (or bumping.) I know some electric starter owner who use the decompression lever with the electric starter, although I do not know whether this is an "approved" method. So, assuming there is nothing wrong with your starter, the only solution is to use a decompression lever to initiate starting. I say this because, and this is a guess, the compression ratio may be high, but I don't think it is wildly high. You are talking about a mechanical compression ratio of 9:1. I don't know when your intake closes, but the corrected compression ratio is probably 8:1. If your combination of parts were to jack up the corrected ratio to 9:1, it would still run well on 92 octane pump gas. If the compression ratio were higher you would hear 'pinking.' I think that attempting to measure the net volume in place is impraticable. The mechanical compression ratio is measured assuming the valves are closed. This is not what occurs. The corrected compression ratio, which starts the calculation when the intake valve closes can be done by formula, but it is always lower than the mechanical compression ratio. This leads me to think that there is something else going on. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Compression ratio
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