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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Top End Speed
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<blockquote data-quote="Martyn Goodwin" data-source="post: 50448" data-attributes="member: 2433"><p>After some more road testing, here is my conclusions.</p><p></p><p>With my standard comet configured as follows: 7.4:1 CP piston, standard head and valves, Mk1 cam, Amal Mk1 premium carb with 105 needle jet and 210 main, original rebuilt Lucas magneto (points at 0.012") with ATD tweaked to give 6 BTDC at starting and 31 BTDC full advance, Wheels front 19" and rear 18" with Michelin Pilot Active tyres 34 psi rear 30 psi front. Spark Plug, gaped at 0.020", is a Nippondenso W22EP-U </p><p></p><p>Front sprocket standard with standard 48 rear sprocket uses standard 108 pitch chain (with rear axle around mid point of adjustment) gives somewhat sedate acceleration and the need to change down to 3rd on some hills. Comfortable top speed of 120 KPH.</p><p></p><p>I then changed the rear sprocket to a 50, the standard 108 pitch chain was OK though the rear axle is now closer to the front of the adjustment, but NOT at the limit of travel. Acceleration is significantly improved and the bike now pulls strongly (in 4th) up most hills where with the 48, 3rd was required. Comfortable top speed is around 118 KPH at what "feels" like the same revs. Sorry I do not have a tacho fitted.</p><p></p><p>The move to a 50 rear sprocket has made the bike much more tractable and pleasant to ride. With a viciously policed Australian speed limit of 100 KPH the variation in top speed is not an issue to me. </p><p></p><p>The Spares Co (UK) as well as Coventry Spares (USA) have the 50 rear sprocket. I believe the chain of choice is Tsubaki 530QR, a quad staked non o-ring chain - make Google your friend to find your local supplier. In Australia I purchased the chain from UMS Transmissions ( <a href="http://www.umstrans.com.au" target="_blank">www.umstrans.com.au</a> ).</p><p></p><p>Hope this info is of some help.</p><p></p><p>Martyn</p></blockquote><p></p>
[QUOTE="Martyn Goodwin, post: 50448, member: 2433"] After some more road testing, here is my conclusions. With my standard comet configured as follows: 7.4:1 CP piston, standard head and valves, Mk1 cam, Amal Mk1 premium carb with 105 needle jet and 210 main, original rebuilt Lucas magneto (points at 0.012") with ATD tweaked to give 6 BTDC at starting and 31 BTDC full advance, Wheels front 19" and rear 18" with Michelin Pilot Active tyres 34 psi rear 30 psi front. Spark Plug, gaped at 0.020", is a Nippondenso W22EP-U Front sprocket standard with standard 48 rear sprocket uses standard 108 pitch chain (with rear axle around mid point of adjustment) gives somewhat sedate acceleration and the need to change down to 3rd on some hills. Comfortable top speed of 120 KPH. I then changed the rear sprocket to a 50, the standard 108 pitch chain was OK though the rear axle is now closer to the front of the adjustment, but NOT at the limit of travel. Acceleration is significantly improved and the bike now pulls strongly (in 4th) up most hills where with the 48, 3rd was required. Comfortable top speed is around 118 KPH at what "feels" like the same revs. Sorry I do not have a tacho fitted. The move to a 50 rear sprocket has made the bike much more tractable and pleasant to ride. With a viciously policed Australian speed limit of 100 KPH the variation in top speed is not an issue to me. The Spares Co (UK) as well as Coventry Spares (USA) have the 50 rear sprocket. I believe the chain of choice is Tsubaki 530QR, a quad staked non o-ring chain - make Google your friend to find your local supplier. In Australia I purchased the chain from UMS Transmissions ( [url="http://www.umstrans.com.au"]www.umstrans.com.au[/url] ). Hope this info is of some help. Martyn [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Comet Top End Speed
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