Author Topic: Timing side anti-syphon valve  (Read 3348 times)

Offline nigeldtr

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Timing side anti-syphon valve
« on: 29.08. 2010 22:12 »
Hello

I am just rebuilding the bottom end of my plunger A10 and I have been advised to clean out and check the anti-syphon valve in the timing side crankcase half, can anyone explain to me what this does?

thanks

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline a10gf

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Re: Timing side anti-syphon valve
« Reply #1 on: 29.08. 2010 22:31 »
Prevents oil emptying from tank to crankcase when engine not running.

Ball stuck \ oil channel blocked = oil starvation.
Spring too loose \ ball not seating properly = wetsump.

A10 GF '53 My A10 website
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Offline RichardL

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Re: Timing side anti-syphon valve
« Reply #2 on: 30.08. 2010 00:16 »
If you haven't already found it, it's behind the oil pump in one of the holes. (Which one, I can't recall right now and no books available while sitting on a plane at the gate.) Poke something in the holes to discover which has a ball and spring in it. You won't be able to service it unless you plan to split the cases. Make sure it's springy. Spray some carb clener in the hole. While I'm thinking about it, it would be interesting to know if anyone has measured the force it takes to compress a new spring a particular amount, and how they did it.

Richard L.
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Offline dpaddock

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Re: Timing side anti-syphon valve
« Reply #3 on: 30.08. 2010 03:25 »
Great photo! Thanks.

David
David
'57 Spitfire


Offline nigeldtr

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Re: Timing side anti-syphon valve
« Reply #4 on: 30.08. 2010 13:15 »
Thank you for the picture - does anyone have a drawing/sketch of the oil ways as I would be interested to know where it "sits" schematically?

Regards

Nigel

1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline a10gf

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Online BSA_54A10

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Re: Timing side anti-syphon valve
« Reply #6 on: 31.08. 2010 06:21 »
Buy a 1/2 dozen springs.
Put them in a bag with a label so that you will remember what they are.
Ever time you pull the pump replace the springs.
Every second that your engine is running hot oil is being drawn through this spring.
A spring is only springie because of the heat treatment that it gets.
With time this spring looses it's proper temper and when it dose you will wet sump.
If you wet sump bad enough there will be no oil in the pump when it starts to spim which is not good for the pump or the rest of your engine.
Bike Beesa
Trevor

Offline muskrat

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Re: Timing side anti-syphon valve
« Reply #7 on: 31.08. 2010 09:07 »
G'day Trevor,
                      wise words, but don't the cases need to be split to change the spring? On A65's it's behind the pump?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Triton Thrasher

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Re: Timing side anti-syphon valve
« Reply #8 on: 31.08. 2010 09:24 »

Ever time you pull the pump replace the springs.
Every second that your engine is running hot oil is being drawn through this spring.
A spring is only springie because of the heat treatment that it gets.
With time this spring looses it's proper temper and when it dose you will wet sump.

None of my engines get that hot.  Even the exhaust valve springs are still springy.

Offline chaterlea25

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Re: Timing side anti-syphon valve
« Reply #9 on: 10.10. 2018 20:00 »
Hi All,
My 2 cents worth is if you have the engine apart modify the anti drain ball /spring to the A65 system
I have posted pictures of this before, then its an easy job to "service" the anti drain

John
1961 Super Rocket
1963 RGS (ongoing)