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A65 Valve springs and collars #773260 05/10/19 6:20 pm
Joined: Jan 2014
Posts: 56
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Samsmc1 Offline OP
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Can anyone tell me what's different between early and later A65 valve springs and their collars? I know BSA changed the size of the valves around 1966, but I think '66 & '67 used the same springs afterward. The spring changed appears to have changed later on. Why?
When I checked availability from Brit Cycles in Canada, they combined the part numbers on both old and new BSA part numbers into a single kit for both styles adding to the confusion.
Thanks
Sam


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Re: A65 Valve springs and collars [Re: Samsmc1] #773266 05/10/19 7:32 pm
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Allan Gill Offline
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I could be wrong but from all the heads I’ve owned the early ones came with thinner gauge steel springs. If you want some decent quality springs drop Ed at E V Engineering a call, his valve springs are second to none and will suit any A65 head. Quite possible the early springs were giving valve bounce or breaking when they started making the spitfire cam more common place.... perhaps

I can’t remember the year but valve collet/keepers changed the angle where the Twain meet. Although I do have a service bulletin somewhere. I’ve never had a problem with the ones I have and like most people I don’t know which angle most of mine are, although I know it’s crucial not to mix them up.


beerchug
Re: A65 Valve springs and collars [Re: Samsmc1] #773297 05/10/19 11:53 pm
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Mark Z Offline
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+1 for E V's springs. I got my last set there. I was especially impressed that they came with a spec sheet.

Allan, I think I know what you mean about the collets. A different angle would position the retainer closer to or farther from the end of the valve stem, right? I've noticed a difference there and thought it was due to wear. I instinctively matched them up though.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: A65 Valve springs and collars [Re: Samsmc1] #773299 05/11/19 12:17 am
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gavin eisler Offline
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IIRC early collets were a simple wedge shape , later were a different angle with a collar, the collar type superceded the earlier. Not sure about unit twins but this happened to unit singles over the same period. Dunno about springs but collets/ keepers changed over the years, change must be complete ,collets , collars and stems are matched.

Last edited by gavin eisler; 05/11/19 1:00 am. Reason: Nickl correction

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 Valve springs and collars [Re: Samsmc1] #773301 05/11/19 12:35 am
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NickL Offline
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On the 71+ a65 etc the collets and top valve cap changed, these must be used as a pair as the included angle
is the difference. This does not affect the valves which are the same as all post 66. Beware of crap pressed
collets, they don't fit anything properly and there were a load of them about.

Re: A65 Valve springs and collars [Re: Samsmc1] #773306 05/11/19 12:55 am
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gavin eisler Offline
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Listen to NickL. I had it half right.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 Valve springs and collars [Re: Samsmc1] #773393 05/11/19 11:19 pm
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NickL Offline
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It's easy to check. Just put 2 collets and the top cap on the valve, grip the valve in one hand and the cap in the other
and put some tension on the assembly. If you can rock the cap without moving the valve then the collets and
cap don't match. With some crap pressed collets they sit right into the cap and only hold on the last 50% or so
of the taper. Although either setup will work for a while, they will be a bitch to remove and/or may fail without warning.


Moderated by  Allan Gill, Jon W. Whitley 

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