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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Big end journal alignment
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<blockquote data-quote="Matty" data-source="post: 22353" data-attributes="member: 1339"><p>Thanks all - I will try to draw some sort of conclusion.</p><p> </p><p>First the Comet big-end journal :-</p><p> </p><p>Big end oil supply seems to be very simple in this case because there is only one "gallery" drilled through the crankpin with one drilling in the bearing journal to it. The oil therefore has only one way to go and I should think the best location for it may be at 12 oclock to gain maximum advantage from the "suction" created by centrifugal force.</p><p> </p><p>For a twin, the situation is more complicated and both the crankpins we have (wrecked one and new one ) have two galleries drilled through them at 180 degree spacing. There is then a drilling to each gallery from each big end journal position - hence four holes in total. </p><p>So with the same pump as the Comet, the oil can go to four different places, implying that there is enough flow to not lose too much oil through the two oil feeds for the big end nearest the feed through the mainshaft before supplying the other big end !!</p><p> </p><p>I still think that in general roller bearing lubrication will be OK provided that there is a good supply of oil and feel that the angular position of the oil holes for the journal should not be critical - after all many other machines just rely on drip feed or splash for a roller big end.</p><p> </p><p>The Rapide that I am working on totally destroyed the rollers for the front cylinder and in fact none were found, just grey metallic dust in the engine, though the con-rod was intact but with the outer big end bearing ring pretty chewed up. The other big end looked fine !!</p><p>With all this rubbish in the engine it has been quite a job to clean it all up and the crankcases have had to be put into a de-greaser and then ( don't tell wives) into the dishwasher.</p><p> </p><p>However there was some blockage in the mainshaft/flywheel oilway which could have restricted the supply to the big ends - though this could have been effect rather than cause.</p></blockquote><p></p>
[QUOTE="Matty, post: 22353, member: 1339"] Thanks all - I will try to draw some sort of conclusion. First the Comet big-end journal :- Big end oil supply seems to be very simple in this case because there is only one "gallery" drilled through the crankpin with one drilling in the bearing journal to it. The oil therefore has only one way to go and I should think the best location for it may be at 12 oclock to gain maximum advantage from the "suction" created by centrifugal force. For a twin, the situation is more complicated and both the crankpins we have (wrecked one and new one ) have two galleries drilled through them at 180 degree spacing. There is then a drilling to each gallery from each big end journal position - hence four holes in total. So with the same pump as the Comet, the oil can go to four different places, implying that there is enough flow to not lose too much oil through the two oil feeds for the big end nearest the feed through the mainshaft before supplying the other big end !! I still think that in general roller bearing lubrication will be OK provided that there is a good supply of oil and feel that the angular position of the oil holes for the journal should not be critical - after all many other machines just rely on drip feed or splash for a roller big end. The Rapide that I am working on totally destroyed the rollers for the front cylinder and in fact none were found, just grey metallic dust in the engine, though the con-rod was intact but with the outer big end bearing ring pretty chewed up. The other big end looked fine !! With all this rubbish in the engine it has been quite a job to clean it all up and the crankcases have had to be put into a de-greaser and then ( don't tell wives) into the dishwasher. However there was some blockage in the mainshaft/flywheel oilway which could have restricted the supply to the big ends - though this could have been effect rather than cause. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Big end journal alignment
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