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#795687 01/15/20 4:16 pm
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Re: BSA A65
I have noticed 2 uninstalled valve spring height differences. 2” outer 1 5/8 inner and 1 5/8” outer and inner. Why the differences and do they have corresponding retainers size difference?
Thanks,
Richard

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1970 Manual says free length inner 1 7/16" ( 36.312 mm)
outer free 1 3/4" ( 44.45 mm).

2" outer (2.03" outer , 1.62" inner ), 1 5/8 inner type was fitted to very early A65 62 -65, these would fit with the early valve / collet arrangement, which changed to a smaller collared collet in later years

SRM supply outer 41.75, inner 39.87 ( triumph type ) ,which is what I now have fitted,

head part numbers change over the years, I dont know if mixing valve springs from early and late will work on any particular head, .I have no experience with the 62 -65 heads/ valves, I dunno if mix n match is OK or not.
Given that the springs got shorter over the years but rockers stay the same I reckon BSA thickened the casting around the valve spring pockets, maybe to allow bigger ports. i know you cant mix n match early collets with late valve spring top keepers and visa versa.

Last edited by gavin eisler; 01/15/20 6:07 pm.

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Quote
i know you cant mix n match early collets with late valve spring top keepers and visa versa.

Problem is. you can physically do that, and yes it's a problem.
Likewise some of the pressed crap colletts that are around.
The wire size changed on later springs, but as you say T120 ones are fine.
Check any for coil bind at fully open as it's hard to know what you've been supplied.
A 60 thou gauge should go into the coils.

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I should have said
"i know you should not mix n match early collets with late valve spring top keepers and visa versa."
Cheers


71 Devimead, John Hill, John Holmes A65 750
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Originally Posted by gavin eisler
...SRM supply outer 41.75, inner 39.87 ( triumph type ) ,which is what I now have fitted...

Hi Gavin,

do you remember which Triumph twin the springs are taken from?
Some years ago, I panicked and gave SRM a call when finding a Triumph sticker on the spring pack and called SRM. I think I had Gary Hearl on the phone who told me this is what SRM considers as suitable for the A 65 as they were shorter and also slightly softer.

Having had issues with worn-off cam shafts before I assembled them with no problems ever since.

So those springs are fine but I have forgotten whether they are originally intended for a T140 or for which model else.

Can you help me out?

Cheers!

Ph.


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Phil
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Sorry Phil cant remember, A T140 is a good bet , I did the same , checked the lengths with the book , WTF , on the phone, bet they are sick of it.Mine work fine too, so far.


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Postage and exchange rate between USA and UK isn't great lately so I have switched to SRM's (race) springs and been happy. I have also used Ed V's springs bought from him in Mitchigan and been quite happy with them


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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I have checked the T140 workshop Manual. It lists the valve springs as outer 41,3 mm (1 5/8") and inner with 38,9 mm (1 17/32").
Those figures are very close to Gavin's measurements so I am inclined to say the valve springs in question are originally for a T140.

As I stated before I have had no issues with those springs that were supplied by SRM.

Cheers!

Ph.


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Phil
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Valve springs have changed throughout the year span of the A50 / A65 and it can be confusing

I would recommend replacing any original valve spring (or new spring), especially if you have different spring readings or heights

Find the correct bottom retainers with the best springs you can purchase

Using Triumph springs by Kibblewhite may do justice

Measure the seat pressure (open and closed) and the installed height, check for coil bind and be on your way


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