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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Valve Timing
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<blockquote data-quote="Matty" data-source="post: 26904" data-attributes="member: 1339"><p>Hi - 15degrees is what you get by moving the mesh of the half-time pinion one tooth with respect to the idler - But what I am trying to say is that this large change seemed to make no difference at all to the performance of my Comet that I could tell.</p><p> So it now runs with the factory settings again instead of roughly equal valve lift at TDC which is what resulted from moving the mesh of the half time pinion one tooth.</p><p></p><p>So playing around with much smaller increments by moving the key on the half-time pinion would seem to be a pointless exercise because the valve timing does not seem to be very critical.</p><p></p><p>I had been through a big exercise on this subject a while ago on the forum - plotting valve lift profiles against crank angle etc. This was in an attempt to find why my bike was not very "pokey" - but all seemed to be OK technically with my set-up. For some reason which has not been resolved, some people with MkIII cams claim they can reach 90mph and cruise at 80 while mine and many other Comets I know struggle to get much over 75mphon a level road.</p><p></p><p>As I said before the lift on my cams is good and I do not think they are significantly worn.</p><p></p><p>If anybody has an answer I would be delighted to know.</p></blockquote><p></p>
[QUOTE="Matty, post: 26904, member: 1339"] Hi - 15degrees is what you get by moving the mesh of the half-time pinion one tooth with respect to the idler - But what I am trying to say is that this large change seemed to make no difference at all to the performance of my Comet that I could tell. So it now runs with the factory settings again instead of roughly equal valve lift at TDC which is what resulted from moving the mesh of the half time pinion one tooth. So playing around with much smaller increments by moving the key on the half-time pinion would seem to be a pointless exercise because the valve timing does not seem to be very critical. I had been through a big exercise on this subject a while ago on the forum - plotting valve lift profiles against crank angle etc. This was in an attempt to find why my bike was not very "pokey" - but all seemed to be OK technically with my set-up. For some reason which has not been resolved, some people with MkIII cams claim they can reach 90mph and cruise at 80 while mine and many other Comets I know struggle to get much over 75mphon a level road. As I said before the lift on my cams is good and I do not think they are significantly worn. If anybody has an answer I would be delighted to know. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Valve Timing
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