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#27233 - 07/11/07 9:26 am Valve timing on A10 rocket cams  
Joined: Apr 2006
Posts: 190
retired-fireman Offline
BritBike Forum member
retired-fireman  Offline
BritBike Forum member

Joined: Apr 2006
Posts: 190
Sydney Australia
Hi all,
I have in my 57 A10 what was supposed to be a 67-356 early rocket/late flash cam. I built this bike back in 1980 and bought the pattern cam from "C&D Auto's" in England. Now I realise A10's are not the fastest bike ever built but this bike has always seemed slugish up top and the exhaust sounds flat, it starts first kick and pulls well down low. Recently it has got the better of me so I have checked the valve timing and the figures I got don't match any cam timings that I can find for the 67-334, 356 or 357.(Checked using .015" lash) IN opens BTDC@37 closes @63 ABDC, Ex opens 73 BBDC then closes 45ATDC. Did BSA supply cam wheels with the keyways cut to suit the rocket/super rocket cams so I could juggle this a bit? Are any of the intermediate wheels or camwheels different? I realise I just might have another junk pattern cam as it is supposed to be a 67-356 grind, info that would help me sort this out would be appreiciated it's been bugging me for years. mad

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#27234 - 07/11/07 12:08 pm Re: Valve timing on A10 rocket cams  
Joined: Aug 2001
Posts: 155
Myles Raymond Offline
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Myles Raymond  Offline
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Joined: Aug 2001
Posts: 155
Glasgow, Scotland
Bill,

First of all, variable timing. BSA produced a one-size-fits-all method of timing the valves for all the A7/10 range. The cam, intermediate and crank gears are all marked so that as long as you line them up you're timed.

They didn't sell anything (different keyways or vernier adjustment) that allowed varying the timing.

Next, the timing figures you've obtained. I have details at home but until then check Dynodave's site for a comparison of results.

http://atlanticgreen.com/bsamain.htm

Regardless of the figures, an A10 with a 356 cam is not a very fast motorcycle though it depends what you're used to by way of comparison. "...this bike has always seemed slugish up top.." is still subjective but probably a fair comment for any Gold Flash.

Myles


Myles Raymond, Glasgow, Scotland.

1932 BSA L32, 1934 BSA R34, 1955 BSA A7ss, 1961 BSA Gold Star, 1954 BSA Daytona twin, 1959 NSU Quickly, 1975 Morini 3 1/2 Sport.

"A tidy workshop is a workshop where no work is ever done" - my Dad.

Moderated by  Allan Gill, Jon W. Whitley 


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