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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
No compression
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<blockquote data-quote="John Appleton" data-source="post: 8190" data-attributes="member: 760"><p>Could this mean we need Tom Thumb?</p><p>A much simpler way(to find your lost compression) is to use a normal piece of garage equipment called a cylinder leak tester. This is a delivery hose which screws into the spark plug hole. A measured amount of compressed air is then passed into the cylinder and the amount leaking past rings , valves etc. is shown as a percentage on the gauge. 20% is an average reading, anything over this is easily pinned down by listening at the exhaust for air leaks, showing a faulty exhaust valve, at the carb for inlet valve, and the breather or open valve cap for rings and piston sealing.</p><p>All of this is done with the cylinder in question on T.D.C. of the compression stroke, having first made sure there is valve clearance.</p><p>Leaks around the head joint are best checked with soap water.</p><p>I would also be checking valve timing as the last time I experienced this type of symptom the front cam shaft had turned in its pinion and I rectified matters by welding it in.</p><p>John</p></blockquote><p></p>
[QUOTE="John Appleton, post: 8190, member: 760"] Could this mean we need Tom Thumb? A much simpler way(to find your lost compression) is to use a normal piece of garage equipment called a cylinder leak tester. This is a delivery hose which screws into the spark plug hole. A measured amount of compressed air is then passed into the cylinder and the amount leaking past rings , valves etc. is shown as a percentage on the gauge. 20% is an average reading, anything over this is easily pinned down by listening at the exhaust for air leaks, showing a faulty exhaust valve, at the carb for inlet valve, and the breather or open valve cap for rings and piston sealing. All of this is done with the cylinder in question on T.D.C. of the compression stroke, having first made sure there is valve clearance. Leaks around the head joint are best checked with soap water. I would also be checking valve timing as the last time I experienced this type of symptom the front cam shaft had turned in its pinion and I rectified matters by welding it in. John [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
No compression
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