Author Topic: A10 Pressure Relief Valve  (Read 2631 times)

Offline Brucie64

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A10 Pressure Relief Valve
« on: 03.03. 2010 22:17 »
Now that the weathers improving I guess its time to dust the cobwebs off the bike and get it serviced ready for the summer at last. However a recent article in well known bike mag got me pondering, it went on about how important a fully functional pressure relief valve is to your stead of choice.

As I have never looked at mine or indeed have ever ever paid it any notice other than to clean the knobbly protuberance next to the timing cover. Can anyone tell a self confessed mechanical idiot like myself how do you know if your relief valve is ok and is doing what it should be do*eek*.

Is there a simply test to put my mind at rest?
Bruce
Spitfire
UK

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Re: A10 Pressure Relief Valve
« Reply #1 on: 04.03. 2010 09:03 »
G'day Bruce,
                 If you can't hear any main or big end noise it must be working !! The only way I know of is to fit a pressure gauge.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

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Re: A10 Pressure Relief Valve
« Reply #2 on: 04.03. 2010 09:11 »
Second thoughts you could make up a jig out of pipe. Screw the OPRV in one end with a hole adjacent to the groove in the OPRV. then fit air line fittings to the other end and use compressor to pump up to 60Lb. It should blow off at 50 Lb. I haven't actually done this but would if I had to test one.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline Brucie64

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Re: A10 Pressure Relief Valve
« Reply #3 on: 04.03. 2010 10:07 »
My thanks Muskrat,

Hopefully I would like to know if it's gone belly up before I start to hear rumblings from down below!. Is there a recommended time at which point you should replace these for peace of mind?
Bruce
Spitfire
UK

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Re: A10 Pressure Relief Valve
« Reply #4 on: 04.03. 2010 10:13 »
Is there a recommended time at which point you should replace these for peace of mind?

Original parts are often better than the new stuff available.

Some people put a Triumph type plunger valve in.  That could be a better valve, but who's to say?

Offline Brucie64

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Re: A10 Pressure Relief Valve
« Reply #5 on: 04.03. 2010 10:28 »
Found some more data on it....

http://www.a7a10.net/oilrelief.htm
Bruce
Spitfire
UK

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Re: A10 Pressure Relief Valve
« Reply #6 on: 04.03. 2010 11:57 »
Good article Bruce, I would be worried if it was fully open at 10 psi. My motors run 50 psi at 2500rpm and 20 psi at idle hot. You could try that jig vertically with oil in the tube and pressurize with air. I'm curious now and will test my spares.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline MikeN

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Re: A10 Pressure Relief Valve
« Reply #7 on: 04.03. 2010 12:18 »
You can always send it off to SRM and they will test it for you.
Mike

Offline Brucie64

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Re: A10 Pressure Relief Valve
« Reply #8 on: 04.03. 2010 12:35 »
Or of course, for peace of mind just buy a new one from SRM.
Bruce
Spitfire
UK

Offline brackenfel

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Re: A10 Pressure Relief Valve
« Reply #9 on: 04.03. 2010 18:52 »
My '61 A10 has the later (A65?) plunger type fitted rather than the one with a ball.. All I've done is simply take it out, clean it, lube it slightly & replace it..
Hopefully that will do, I can't see much point in buying an expensive but rather similar new one...
1961 A10 650 Golden Flash - Blue
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Offline dpaddock

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Re: A10 Pressure Relief Valve
« Reply #10 on: 04.03. 2010 23:14 »
Remove the PRV from the engine, clean it and inspect it. It he ball is still round and the spring is still in one piece, reinstall the assembly and go on your way. Note that the PRV is there to protect the big ends and mains: it opens when oil pressure for them is satisfied and it then directs the excess to go to the camshaft gallery. Which is why some wag states that the camshaft has "part time lubrication."

But, don't worry about it: BSA made a good system.

Make sure you change the engine oil often to keep the internals clean.

IMOH all this SRM worship is unnecessary.

David
David
'57 Spitfire


Offline Brucie64

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Re: A10 Pressure Relief Valve
« Reply #11 on: 05.03. 2010 10:13 »
I agree David, I have just looked at the SRM price for the PRV and decided against it. I will as you suggest lop it out and give it a gander with the old Mk1 eyeball. Hopefully if all is well I will just slot it back in and be on my way.

Thanks Again.
Bruce
Spitfire
UK

Offline A10Boy

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Re: A10 Pressure Relief Valve
« Reply #12 on: 05.03. 2010 13:32 »
You can buy a kit with ball, spring and fibre washers. Clean the gauze on the front, check the ball seat and if its in good shape you can reassemble making sure its perfectly clean. Also, dont be tempted to over tighten it into the crank case.

The main thing to keep it in good nik is regular oil changes. If any crud gets stuck under the ball, you will loose pressure to the big ends and bang... [another reason not to over do the blue hylomar]
Regards

Andy

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