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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Oil Use
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<blockquote data-quote="Martyn Goodwin" data-source="post: 46558" data-attributes="member: 2433"><p>Current Situation:</p><p>The timed breather spindle ET159 is in place but the timed breather pinion ET141/n is missing. At the timed breather outlet on the side of the motor I have installed a modified banjo that provides a 1/2" od copper pipe outlet connected to a short length of 1/2" ID hose that in turn connects to a home made damping chamber consisting of a 2 1/2 inch length of 1 1/2 inch bore PVC pipe. The pipe is loosely filled with stainless steel spiral scouring pad material and the end caps on the pipe have a 1/2 inch OD pipe fitted to them. From the banjo the hose and damper run vertically (up behind the carb) with the outlet of the damper then connecting to a Bunn (or if you prefer PCV) valve. The outlet of this is connected to a hose that eventually exits at the rear of the bike. Theory is that the damper diameter slows down the gas flow and then the scouring pad stuff knocks the oil out of suspension. The Bunn only opens in response to positive crankcase pressure when the piston is descending then seals tight creating a partial vacuum in the crankcase when the piston is ascending.</p><p></p><p>This works as intended and the oil is indeed removed from the gas stream by the home made damper - but the tight sealing Bunn valve prevents the oil being drawn back into the motor by the partial vacuum. If I run the bike for less than 3/4 hour no oil escapes from the breather outlet - instead it accumulates inside the damper. If I run it for much longer than 45 minutes I start to get some oil loss out of the end of the breather.</p><p></p><p>Next Steps:</p><p>I am attempting to source an Elephants Trunk breather - Kemps' no longer supply them but I am (very) hopeful of obtaining one from Mac Read (see MPH #502). If that fails I will put a leak down tube into the line between the Bunn valve and the Damper chamber. The leak down tube will have a bore no greater than 1/16 inch and will run vertically upwards for a few inches to atmosphere; the idea being that the leak down tube will be too small to allow oil out when the piston is descending but will be of sufficient size to allow the vacuum caused by the piston moving up to draw in some air allowing any oil in the damping chamber to return to the motor.</p><p></p><p>M</p></blockquote><p></p>
[QUOTE="Martyn Goodwin, post: 46558, member: 2433"] Current Situation: The timed breather spindle ET159 is in place but the timed breather pinion ET141/n is missing. At the timed breather outlet on the side of the motor I have installed a modified banjo that provides a 1/2" od copper pipe outlet connected to a short length of 1/2" ID hose that in turn connects to a home made damping chamber consisting of a 2 1/2 inch length of 1 1/2 inch bore PVC pipe. The pipe is loosely filled with stainless steel spiral scouring pad material and the end caps on the pipe have a 1/2 inch OD pipe fitted to them. From the banjo the hose and damper run vertically (up behind the carb) with the outlet of the damper then connecting to a Bunn (or if you prefer PCV) valve. The outlet of this is connected to a hose that eventually exits at the rear of the bike. Theory is that the damper diameter slows down the gas flow and then the scouring pad stuff knocks the oil out of suspension. The Bunn only opens in response to positive crankcase pressure when the piston is descending then seals tight creating a partial vacuum in the crankcase when the piston is ascending. This works as intended and the oil is indeed removed from the gas stream by the home made damper - but the tight sealing Bunn valve prevents the oil being drawn back into the motor by the partial vacuum. If I run the bike for less than 3/4 hour no oil escapes from the breather outlet - instead it accumulates inside the damper. If I run it for much longer than 45 minutes I start to get some oil loss out of the end of the breather. Next Steps: I am attempting to source an Elephants Trunk breather - Kemps' no longer supply them but I am (very) hopeful of obtaining one from Mac Read (see MPH #502). If that fails I will put a leak down tube into the line between the Bunn valve and the Damper chamber. The leak down tube will have a bore no greater than 1/16 inch and will run vertically upwards for a few inches to atmosphere; the idea being that the leak down tube will be too small to allow oil out when the piston is descending but will be of sufficient size to allow the vacuum caused by the piston moving up to draw in some air allowing any oil in the damping chamber to return to the motor. M [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Oil Use
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