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Old 27-11-17, 05:47 PM   #1
Linecaster
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Default Testing Plug Lead

I am trying to restore a Villiers Mk20. After freeing and grinding in the valves, taking the flywheel off and cleaning and regaping the points I now have compression and a spark.

When I got the engine it did not have a carb. I found one at Oakley but on inspection at home found it did not have a float, a fuel needle or a needle lever. I have now obtained parts for carb so thought I would give it a swing. First pull it fired once (much to my surprise) but can only get it to give an occasional single cough. Changed plug with same result. Also cannot get it to fire if I put petrol down plughole.

On testing the plug lead could not get an Ohms reading. On inspection the lead has a spring and a carbon rod on the end (see photo). Tested the lead without the carbon rod and got a reading. Tested the carbon rod and cannot get an ohms or continuity reading through it.

Can anyone tell me if I should get a reading from the carbon rod. As I said I am getting a spark at the plug (I have seen better on other engines) but it doesn't look too weak.

Any help would be appreciated.
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Old 27-11-17, 07:12 PM   #2
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Not really knowing what to expect from an HT pickup brush, I've just measured one and got a 'wobbly' 3 ohms or so (varies with probe contact area and pressure). Then I thought why would a Villiers flywheel mag use one anyway as there is no relative movement between the pickup and coil? So pulled one out of a likely looking Mar-Vil and found just a little brass top hat - see attached pic.

NHH
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Last edited by nickh; 27-11-17 at 07:42 PM. Reason: sp
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Old 28-11-17, 10:50 AM   #3
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All my Villiers had/have a similar arrangement to that shown in Nicks photo.
Notice that the spring is attached to the lead by a small screw that is screwed into the strands of wire inside the lead. Maybe yours is missing the internal screw so the rod is not contacting the wire core.

I have made my own up from new lead

http://www.gsparkplug.com/100-meter-...lon-black.html

a spring from an old ball point pen

and a short piece of brass rod.
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Old 28-11-17, 12:03 PM   #4
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Quote:
Originally Posted by woodsman View Post
All my Villiers had/have a similar arrangement to that shown in Nicks photo.
Notice that the spring is attached to the lead by a small screw that is screwed into the strands of wire inside the lead. Maybe yours is missing the internal screw so the rod is not contacting the wire core.

I have made my own up from new lead

http://www.gsparkplug.com/100-meter-...lon-black.html

a spring from an old ball point pen

and a short piece of brass rod.
I think I understand how you've assembled it, but a photo when you have time would confirm thanks.

Stuart.
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Old 28-11-17, 04:45 PM   #5
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Default Is it the right setup

There is a brass screw going up inside the lead that the spring touches. I have checked that this makes contact with the wire.
Perhaps I ought to use a brass rod instead of the carbon one.
Anyone got an exploded view of the plug lead connection to the coil on a Villiers which might show if mine is the wrong setup?
Cheers Linecaster
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Old 28-11-17, 05:05 PM   #6
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Quote:
Originally Posted by Linecaster View Post
(snip)
Perhaps I ought to use a brass rod instead of the carbon one.
Or at least find a piece of 'carbon' which actually conducts!

NHH
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Old 28-11-17, 05:52 PM   #7
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I wonder if one of these would work?

Stuart.
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Old 29-11-17, 04:09 PM   #8
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Sorry - bit out of focus
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Old 29-11-17, 05:40 PM   #9
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Quote:
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Sorry - bit out of focus
Thanks, due to lack of a lathe (and no skill to drive one) I wonder if a suitably sized brass cheesehead bolt with the head filed flat would work?.

Stuart.
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Old 29-11-17, 10:11 PM   #10
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Thanks for suggestions and pictures.
I'll try making a brass replacement for carbon brush and let you know results when I've tried it.
Cheers Linecaster
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