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8e magneto back plate

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8e magneto back plate

Post  alan67 on Tue Mar 20, 2018 8:34 pm

Hi guys  as i'm cleaning my magneto back plate i notice a long thin brass screw [see pic ] can any one tell me its purpose   thanks in anticipation Alan
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screw

Post  piston 197 on Wed Mar 21, 2018 6:58 am

It will have a hole through the length of it and is a breather
JH
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Re: 8e magneto back plate

Post  alan67 on Wed Mar 21, 2018 8:34 am

piston 197 wrote:It will have a hole through the length of it  and is a breather
JH
thanks John
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8E magneto back plate vent

Post  keith livingstone on Thu Mar 22, 2018 7:23 pm

Hello Alan
Good to hear from you again
I take it you're progressing well with the Falcon 67?

Fake News
I had a guy show me his similar James Captain and he pointed out the vent and said it was a pretty neat way of making a fine adjustment to the ignition timing. I said nothing!

Best wishes and good progress with the 67
Keith
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8E magneto back plate vent

Post  keith livingstone on Thu Mar 22, 2018 7:30 pm

Hi Alan

Just noticed from the picture of the backplate yours must be a fairly early 8E!
If you look at the lighting coils these only have 2 fixing points. Very soon after your engine was made I believe Villiers introduced 2 additiona supports under the back plate and nearly all 8E's have lighting coils with 3 fixing points.

Best wishes
Keith


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Re: 8e magneto back plate

Post  bill2b on Thu Mar 22, 2018 9:32 pm

I don't dispute it being a breather but is it really necessary, surely there is plenty of gaps around the flywheel cover to let it breath? Neutral
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Re: 8e magneto back plate

Post  piston 197 on Fri Mar 23, 2018 5:28 am

bill2b wrote:I don't dispute it being a breather but is it really necessary, surely there is plenty of gaps around the flywheel cover to let it breath?  Neutral

You would think so, there used to be a sealing ring inside the cover, like a large thin rubber band and then the breather was necessary, but no one seems to fit it.
Years ago a friend of mine called Gareth used to use an old piece of inner tube around the flywheel cover to make his trials bike ignition waterproof. his crankcase seal was leaking, ,the flywheel was subjected to patrol vapour and the points caused a spark followed by an explosion which blew the cover off and straightened out his gear lever.
So yes in this case a breather would have been useful !

JH
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8e magneto back plate

Post  alan67 on Fri Mar 23, 2018 3:35 pm

Hi Keith,Bill John after John informed me about the breather tube it made sense , unscrew the tube,blow it out now and again ,all is well i was going to make a rubber seal for the flywheel cover but after reading about John;s mate i will let mine have some fresh air, even though my crank seal are new. as for progress i had been working on all the steel work and all is in primer ready for colour but with the present cold weather i have turned my attentions to the engine, i will post some pic's when i get a few things finished thanks all Alan
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Breather

Post  piston 197 on Fri Mar 23, 2018 3:45 pm

When the cover is sealed completely and there is no breather there is the liklihood of condensation inside the electrics which is never good, the breather is there to prevent this condensation occurring as the cold air inside the cover is heated by the engine,
When i first started trialling on an Ossa circa 1974 the cover had a breather on the top which when submerged in water,drew water in, the failure to finish in my very first trial, the answer was to put a piece of long petrol pipe onto the breather and run it up the frame and tape it to the top tube.
With the Ossa there were no points, just a Moto-plat electronic ignition unit which relied on a very small air gap between the rotor and stator for it to work, even the slightest of moisture in here caused it to stop, often the heat from the engine dried it out in about 20 minutes and it would go again, but the bit of pipe on the breather was the answer and never had a problem again
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Breather

Post  kerabo on Fri Mar 23, 2018 4:17 pm

piston 197 wrote:
bill2b wrote:I don't dispute it being a breather but is it really necessary, surely there is plenty of gaps around the flywheel cover to let it breath?  Neutral

You would think so, there used to be a sealing ring inside the cover, like a large thin rubber band and then the breather was necessary, but no one seems to fit it.
Years ago a friend of mine called Gareth used to use an old piece of inner tube around the flywheel cover to make his trials bike ignition waterproof. his crankcase seal was leaking, ,the flywheel was subjected to patrol vapour and the points caused a spark followed by an explosion which blew the cover off and straightened out his gear lever.
So yes in this case a breather would have been useful !

JH

Nice one
I sort of guessed what was coming as I read this.

Where does it come out on the inside. In the points?

Ken
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where does it come out ??

Post  piston 197 on Fri Mar 23, 2018 4:23 pm

It does not come out anywhere ? there is just a threaded through hole in the back plate, and the breather tube just screws into this threaded hole to allow passage of air from inside the casing to the outside atmosphere, obviously as the air inside the cover heats up it will expand slightly without the breather, if there is an airtight seal the breather allows for the air to pass freely.
JH
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Re: 8e magneto back plate

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