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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
How Much Compression Reading Should A Twin Have & Leak Down
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<blockquote data-quote="CarlHungness" data-source="post: 173870" data-attributes="member: 2517"><p>There are about 16 pages on this forum of sincere replies to my dilemma of trying to get my Shadow running and the problem(s) are beyond my capabilities and seemingly defy logic.</p><p> As one of my last resorts I did a compression test and the best I can get is 90 lbs,(with throttle wide open) which is the same as I recall getting a decade ago. Since, I've had new pistons, rings, valve job (by journeyman Glenn Bewley in the US) and it HAD been running well ever since. John Healy from Coventry says 150 lbs are needed to fire the machine. I don't think I've ever had over 90 during my ownership. I'd never taken a leak down test on any engine, so bought a tester that has no instructions but seems straightforward. I put the piston near TDC, hooked up the air hose to the tester and watched the gauges. I got an immediate 100%, and watched the second guage ever-so-slowly depress, and one can surmise there just isn't any leakage coming from the rings or valves.</p><p> Compression seems to be the same as it has been in the past as I can stand on the kickstart lever and she won't go over TDC without the decomp. So am wondering what the 'normal' lbs would be on a twin.</p><p> The 3-4 times I have made the bike fire it has run for 15 to 60 seconds and seems like it runs out of fuel. The mag is newly rebuilt last week by Doug Wood, I've timed and re-timed and re-timed and made sure the ATD has stayed open, an on and on to the point of madness. So very many members have given me advice and I'm about knackered in trying to get to the bottom of the problem, so had to do the compression/leak-down test.</p></blockquote><p></p>
[QUOTE="CarlHungness, post: 173870, member: 2517"] There are about 16 pages on this forum of sincere replies to my dilemma of trying to get my Shadow running and the problem(s) are beyond my capabilities and seemingly defy logic. As one of my last resorts I did a compression test and the best I can get is 90 lbs,(with throttle wide open) which is the same as I recall getting a decade ago. Since, I've had new pistons, rings, valve job (by journeyman Glenn Bewley in the US) and it HAD been running well ever since. John Healy from Coventry says 150 lbs are needed to fire the machine. I don't think I've ever had over 90 during my ownership. I'd never taken a leak down test on any engine, so bought a tester that has no instructions but seems straightforward. I put the piston near TDC, hooked up the air hose to the tester and watched the gauges. I got an immediate 100%, and watched the second guage ever-so-slowly depress, and one can surmise there just isn't any leakage coming from the rings or valves. Compression seems to be the same as it has been in the past as I can stand on the kickstart lever and she won't go over TDC without the decomp. So am wondering what the 'normal' lbs would be on a twin. The 3-4 times I have made the bike fire it has run for 15 to 60 seconds and seems like it runs out of fuel. The mag is newly rebuilt last week by Doug Wood, I've timed and re-timed and re-timed and made sure the ATD has stayed open, an on and on to the point of madness. So very many members have given me advice and I'm about knackered in trying to get to the bottom of the problem, so had to do the compression/leak-down test. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
How Much Compression Reading Should A Twin Have & Leak Down
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