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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Breathers
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<blockquote data-quote="davidd" data-source="post: 45208" data-attributes="member: 1177"><p>Fair enough, you've got me there. But I would argue that this is a really poor vent pipe. There is no effort to separate the oil from the air as in the oil cap vent (and even that fails at high revs.) So, you have your choice of a vent pipe that passes oil and deposits it on your chain or a metered oil pipe that deposits an inconsistent amount of oil on your chain. I will say that there is rarely a catastrophic condition caused by high pressure in the oil tank, as far as my experience goes. On the other hand, pressure in the crank case is almost always caused by ring leakage. </p><p></p><p>Taking the major cause as ring leakage, the timed breather is at a distinct disadvantage. It works well only if your rings work well because it is mechanically closed even if the pressure in the crank case remains high. Racers can also have ring flutter at high rpm's and cause momentary instances of high pressure. The check valve breathers work well at low rpm's, but the higher the rpm's the worse they get. Sometimes the ball is too heavy to match its cycle to the pressure cycle. However, for normal street riding they seem to work well and they are inexpensive. </p><p></p><p>On the racer I have used both the timed breather, which worked flawlessly, and a Ducati reed valve breather, which also worked flawlessly. However, I check my valves and ring leakage quite a bit with the much loathed leak-down tester.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 45208, member: 1177"] Fair enough, you've got me there. But I would argue that this is a really poor vent pipe. There is no effort to separate the oil from the air as in the oil cap vent (and even that fails at high revs.) So, you have your choice of a vent pipe that passes oil and deposits it on your chain or a metered oil pipe that deposits an inconsistent amount of oil on your chain. I will say that there is rarely a catastrophic condition caused by high pressure in the oil tank, as far as my experience goes. On the other hand, pressure in the crank case is almost always caused by ring leakage. Taking the major cause as ring leakage, the timed breather is at a distinct disadvantage. It works well only if your rings work well because it is mechanically closed even if the pressure in the crank case remains high. Racers can also have ring flutter at high rpm's and cause momentary instances of high pressure. The check valve breathers work well at low rpm's, but the higher the rpm's the worse they get. Sometimes the ball is too heavy to match its cycle to the pressure cycle. However, for normal street riding they seem to work well and they are inexpensive. On the racer I have used both the timed breather, which worked flawlessly, and a Ducati reed valve breather, which also worked flawlessly. However, I check my valves and ring leakage quite a bit with the much loathed leak-down tester. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Breathers
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