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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Identifying cams
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<blockquote data-quote="davidd" data-source="post: 178635" data-attributes="member: 1177"><p>Nobby,</p><p></p><p>I would presume the lightened cam is a Mk2, or at a minimum, a larger profile cam. As most owners know, you have to modify the decompressor spindle boss in the timing chest to run a large lift cam like the Mk2. If that work has been done, it is likely a Mk2.</p><p></p><p>I should note that lightning timing chest gears is always a serious mistake. The engine will produce less power at the higher RPMs. This is because Phil Irving calculated the timing gears, particularly the cam pinion, to have precisely the correct mass to damp vibrations caused by the reciprocating valve action. If the pinions are lightened the valves tend to move erratically as they speed up and sap power from the engine. These results have been proven on the Spintron by top-name sprinters.</p><p></p><p>Save your money and time and stick to buying a nice cam. The Megacycle Mk2 is a very nice cam. It was originally designed by Andrews and purchased by Megacycle. Megacycle may have modified it some, but it produces about 40 HP per cylinder with 10:1 compression, and is a relatively low lift (it does need the Mk2 clearance in the timing chest). It has proven to be very reliable.</p><p></p><p>At 0.050" lift:</p><p></p><p>IO 37</p><p>IC 51</p><p>EO 51</p><p>EC 37</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 178635, member: 1177"] Nobby, I would presume the lightened cam is a Mk2, or at a minimum, a larger profile cam. As most owners know, you have to modify the decompressor spindle boss in the timing chest to run a large lift cam like the Mk2. If that work has been done, it is likely a Mk2. I should note that lightning timing chest gears is always a serious mistake. The engine will produce less power at the higher RPMs. This is because Phil Irving calculated the timing gears, particularly the cam pinion, to have precisely the correct mass to damp vibrations caused by the reciprocating valve action. If the pinions are lightened the valves tend to move erratically as they speed up and sap power from the engine. These results have been proven on the Spintron by top-name sprinters. Save your money and time and stick to buying a nice cam. The Megacycle Mk2 is a very nice cam. It was originally designed by Andrews and purchased by Megacycle. Megacycle may have modified it some, but it produces about 40 HP per cylinder with 10:1 compression, and is a relatively low lift (it does need the Mk2 clearance in the timing chest). It has proven to be very reliable. At 0.050" lift: IO 37 IC 51 EO 51 EC 37 David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Identifying cams
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