Author Topic: 1951 A7 pressure relief valve  (Read 474 times)

Offline Rex

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1951 A7 pressure relief valve
« on: 23.12. 2017 11:18 »
Hi all, many A7/10s seem to have the dome-headed Triumph type PRVs fitted in place of the flat-topped item my engine has. I have a nice spare ex-Trumpet unit to use if they're compatible.
I know the BSA has a ball and spring (BSA loved their balls and springs) whereas the Triumph has a spring and piston, but has anyone actually done the swap?

Offline muskrat

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Re: 1951 A7 pressure relief valve
« Reply #1 on: 23.12. 2017 12:33 »
G'day Rex.
I haven't but quite a few have.
https://www.a7a10.net/forum/index.php?topic=12120.msg94825#msg94825
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Online JulianS

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Re: 1951 A7 pressure relief valve
« Reply #2 on: 23.12. 2017 13:41 »
I fitted an SRM PRV some time ago and very happy with it.

You do need to be careful if you fit a piston type PRV if you do not know what it was originally made for.

There are a least 3 types;

Twin and earlier unit single type set a 50 PSI blow off pressure

Triple type set at 70 PSI blow off

Late unit single set at 75 PSI blow off.

BSA issued some service sheets as photos.

Offline Rex

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Re: 1951 A7 pressure relief valve
« Reply #3 on: 24.01. 2018 11:04 »
To answer my own question, SRM apparently supply the same item for A7/10s and a whole range of triumph twins, so it looks like they're interchangeable.

Offline RichardL

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Re: 1951 A7 pressure relief valve
« Reply #4 on: 24.01. 2018 11:29 »
If you are sure you have the Triumph vs. A10 version,  a call to Gary Hearl at SRM would settle the question as to if they are equivalent in function.

Richard L.
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Online Greybeard

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Re: 1951 A7 pressure relief valve
« Reply #5 on: 24.01. 2018 13:39 »
My bike engine is using the SRM piston style PRV.