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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Smoking After Rebore Is the Bore Glazed ?
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<blockquote data-quote="Matty" data-source="post: 62207" data-attributes="member: 1339"><p>Thanks Vibrac -my engine did not seem to smoke on a regular basis when I started and more by luck than judgement I noticed that when I checked the oil and found that sometimes the level had dropped half a pint or so due to sumping it not unnaturally smoked but I also noticed that if the engine had been left near TDC it did not seem to sump.</p><p>I found a reference on the Norton forum which said this was a known effect due to the crankpin being at its highest level at TDC which reduced the sumping greatly, because oil does not naturally travel uphill.</p><p>With our Comets the oil will drain from the oil filter as above at bottom dead centre but of course even at TDC some will drain from the filter and dribble out of the Quill directly into the sump - but hopefully not too much. </p><p></p><p>I am not sure how oil leaks past the pump into the filter but a combination of wear and the rest positions of the pump ports could account for this and its irregular happening.</p><p></p><p>I feel that some oil will inevitably end up in the bottom of the crankcase however, because some will come from the oil filter and leak out of the quill - this I think would be about half the filter capacity - my Comet seems to collect around 150cc overnight but the loss from the oil tank does not get more in the short term if the engine is left at TDC. The 150cc does not seem to cause much if any smoke on startup and is probably just oil lurking in dark corners after running.</p><p></p><p>I feel the jury is still out on the TDC trick and I would be very interested if anybody else has found that this helps, or if not enough data has been collected to prove anything yet.</p><p></p><p>PS In most cases the engine will naturally stop near compression on a single, so perhaps that is also why sumping is a comparativly irregular event !!</p><p></p><p>Matty</p></blockquote><p></p>
[QUOTE="Matty, post: 62207, member: 1339"] Thanks Vibrac -my engine did not seem to smoke on a regular basis when I started and more by luck than judgement I noticed that when I checked the oil and found that sometimes the level had dropped half a pint or so due to sumping it not unnaturally smoked but I also noticed that if the engine had been left near TDC it did not seem to sump. I found a reference on the Norton forum which said this was a known effect due to the crankpin being at its highest level at TDC which reduced the sumping greatly, because oil does not naturally travel uphill. With our Comets the oil will drain from the oil filter as above at bottom dead centre but of course even at TDC some will drain from the filter and dribble out of the Quill directly into the sump - but hopefully not too much. I am not sure how oil leaks past the pump into the filter but a combination of wear and the rest positions of the pump ports could account for this and its irregular happening. I feel that some oil will inevitably end up in the bottom of the crankcase however, because some will come from the oil filter and leak out of the quill - this I think would be about half the filter capacity - my Comet seems to collect around 150cc overnight but the loss from the oil tank does not get more in the short term if the engine is left at TDC. The 150cc does not seem to cause much if any smoke on startup and is probably just oil lurking in dark corners after running. I feel the jury is still out on the TDC trick and I would be very interested if anybody else has found that this helps, or if not enough data has been collected to prove anything yet. PS In most cases the engine will naturally stop near compression on a single, so perhaps that is also why sumping is a comparativly irregular event !! Matty [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Smoking After Rebore Is the Bore Glazed ?
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