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Collection, Preservation and Display of Old Lawn Mowers

Villiers Mk25

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Hi,

Many thanks for letting me join your group.

I have inherited a vintage 36" Atco with a Villiers Mk25 engine. I have read threads on this forum how to set up the timing and points and fully understand this information. However I can't find information on the coil wiring.

I have fitted a new condenser to try and get the engine to run but am confused by the coil wiring.

There is a feed wire that runs from the coil to the positive side of the points. This side of the points is insulated from the points housing and the backing plate. The wiring is original and I am confused why there is a soldered wire that come from the same point of the coil and fixed to the back plate? This is earthing out the live side of the points permanently! Is this correct?

I look forward and appreciate any help and advise.

regards

Nick 

Forums

wristpin Tue, 18/10/2016

Welcome,

The coil primary winding is earthed at one end - usually through its core or laminations and connected to the insulated terminal on the points at the other, but in some applications the coil primary has a short fly lead to Earth it to the back plate - quite often uninsulated .  What you haven't mentioned is the condenser or capacitor which  may be hidden below the points box and will have a single wire to the insulated terminal on the points.

I'll see if I can find a decent diagram or schematic and add it to this post later.

This is the best that I can find but it does show the various ignition components.

https://www.dropbox.com/s/6ug13v988r52l8n/Villiers%20Mk25%20ignition000…

Have just re-read your original post and see that you did mention the condenser, but it belatedly occurs to me that the wire that you mention as apparently going to earth may in fact be the kill wire that actually goes to an insulated terminal on the back plate. This may either be connected to a conventional switch mounted on the handlebar of the machine or or to a spring loaded cutout button on the outside of the magneto back plate. Part numbers 34 - 39 on the scan .

https://www.dropbox.com/s/k5zvcvf4mktnktr/Villiers%20Mk25%20mag%20part%…

Nick_Rigler Wed, 19/10/2016

Hi, 

Many thanks for your reply and information.

I think with all the information you have provided I will be able to fix the issue. 

The kill switch wiring does not seem to be insulated to the back plate and the wiring from the rear of the back plate to a switch is missing. This is what was confusing me.

Ill have another look at the weekend and and let you know how I get on.

Once again, many thanks

Nick

wristpin Wed, 19/10/2016

I think that it is unlikely that the insulation would have been removed and it's termination then reassembled, so have a good look. The insulation is only a small "top hat" and flat fibre washer so may not be immediately obvious and not all machine manufacturers fitted an external switch.. 

 

Nick_Rigler Wed, 19/10/2016

Thanks for your help, I found the problem now . The wire for the kill switch from the coil  had damaged insulation below the coil and it was earthing out on the back plate.

replaced the wire and everything is fine now.

just need to fit it back onto the engine and

time it up.

many thanks 

wristpin Wed, 19/10/2016

A satisfactory result.  Just in case, set the points gap to between 12 and 16 thou and then the timing to 3/16 of an inch of piston travel before top dead centre.