Villiers Mk 10 weak spark

Hi, I'm a newbie to stationary engines (you may have seen my 1st posts re 'what pump ?').
Whilst I know a bit from my tinkerings on Anglias, Cortinas and the like, magnetos are new to me.
My 1st venture, a Villiers mk 10 won't fire up.
I've cleaned carb, checked the points gap and attempted to clean them thro' the flywheel.
It does spark however it is weak. Ignition lead to earth sparks - weakly- but I can only get the plug to spark by reducing the gap to 3-4thou and that is outside the pot of course.
I'm assuming timing is near enough and guess it would have to be a mile out to affect spark strength so I suspect coil. I measured 3.7ohms at HT lead/earth which I guess is about right but doesn't tell me much about it's health
The plug by the way, a Champion L86 fires up my lawnmower ok (screwed in part way as it's a longer plug) so that's ok.
Before I take flywheel off, does anybody know of anything else worth trying. I just have this thing about wanting it to fire up before I properly restore !
Also can I test the coil/spark with a battery ? Of course I want to be sure before I lash out with my 1st spares purchase.
thanks Steve

If the points are clean and gapped correctly and you have a clean, known good plug then my money would be on the coil. Old Villiers coils are well known for breaking down over time. Replacements are available, but are not what you might call cheap: https://villiersservices.co.uk/index.php?main_page=index&cPath=8_18_52

I believe the only way to properly test them is on proper rig.

My advice, if you intend to continue with this mad hobby, would be to invest in a cheap digital multimeter. In the meantime a simple continuity test will surffice. Using 6/12 volt bulb, battery and a couple of bits of wire check for continuity between HT button and 'earth'. As Matt says HT winding is likely open circuit but the voltage is jumping the gap internally. I am not at home but I think plug gap should be 25 thou. No doubt someone else can confirm.

Muppet! Didnt read your previous carefully!
I'd expect 4.5 - 5K so maybe HT is shorting somewhere. Are you sure you had selected correct range?

I/d get flywheel of get them points out clean and polish refit change the condenser refit and try again
good luck

Thanks again for input. Getting somewhere now - more fun !
Got the flywheel off. To confirm some numbers...measured with an auto-ranging meter.
lifted Lt lead to earth 1.0 ohm
lifted HT lead to earth 3.8 ohm - yep I would expect kilohms.
lifted HT lead to LT lead 3.8 ohm - strange - why not 4.8 ?
Condensor measures open circuit as I would expect.
The bigger surprise is that the M shaped core of the coil has been rubbing on the full circumference of the flywheel across the magnets. (The magnets are still magnets by the way) The plates are distorted, the flywheel is scored and what I would describe as heat marks on tip of plates. It's full circumference on wheel so probably not an eccentrity problem.
So it is still looking like an expensive coil replacement (that bit is not fun ) . What is bugging me is if I do that I don't know what the clearance on the plates to flywheel should be, it's not adjustable, and I can't see any way of checking it on refit. Any thoughts please ?

I forgot to add - the mounting holes for the magneto backplate have raised edges as though there has been some lateral movement, though plate and flywheel were tight on removal

what do you mean by plates, any pictures.
Maryalice

Oh dear !!
Distorted backplate and scored flywheel doesn't sound good. There is no adjustment for backplate position. If the backplate mounting holes are worn maybe it was loose and wandering around.  If you put it back together and tighten securely, can you feel/hear it rubbing when spun over quickly using pull rope?

Either way it sounds like spending money on a coil isn't a good idea until you have determined the cause of the wear and sorted it. Backplate and flywheel do come up on fleabay but it may turn out to be a pricey restoration.

maryalice wrote:what do you mean by plates, any pictures.
Maryalice

The laminated plates in the magneto?

Was there any indication of rubbing when you pulled it over to check the spark? The backplate is secured by a countersunk screw as well as the nuts IIRC, seems strange for it to come loose. Could it be that a foreign object has found it's way in?

Thinking about this last night in bed (yeah, I know I'm sad...), the magneto backplate carries the main bearing on that side so even if the backplate was loose the flywheel would move with backplate. What condition is the bearing in?

Sorry think I mislead you there, the backplate I referred to is the one the coil/laminates are rivetted to. You can see in the photo the burrs around the mounting hole and the state of the laminations. I think this may be a later Mk 10 as this particular item looks different to my Mk10/Mk 12 manual.
It was firmly mounted when I dismantled. Not sure if it's been loose at some time before I bought it.

Re model, no engine plate on the cowl?  
Looking at the coil I would guess MK10/2 but original would have Villiers on it
I think Matt could be right. I wonder if the magneto side bearing has collapsed and allowed the crankshaft to bounce around. Time to strip down - even  if it turns out to be a scrapper a least you can salvage some spares.
That said I may have something in the shed which would help. First thing to do is to have it to bits and assess the mechanical damage.

I think I have the parts from a C12, are they the same?, although the coil is probably dead I think it is a separate part?

mattblack wrote:I think I have the parts from a C12, are they the same?, although the coil is probably dead I think it is a separate part?

They do look similar in the manuals but wasn't the C12 'electronic' ignition. Any identifying marks Steve?

Woodsman wrote:

They do look similar in the manuals but wasn't the C12 'electronic' ignition. Any identifying marks Steve?

I think maybe the late ones were, the one my bits are from was definitely points as I enquired about converting it to electronic. The one on my pump is points as well.

No marking on engine. The ignition assembly in photo is Wipac Assy41079/1. The flywheel is marked A60079 65/-8 73 . What I thought were burrs now appear to be inserts in the mounting holes, could these be original or maybe a repair ? The bearing does feel rigid and I've put the assembly back to check fit and with masking tape on inner diameter of flywheel the laminate core is not rubbing the flywheel -is a couple of thou typical clearance I wonder ? Maybe previous owner fixed the rub problem but not the coil..
Just going back to coil resistance, I've read somewhere that LT side has to be lifted to measure HT. If so I don't understand why that is as HT lead to ground (even with points open) seems to me should be kilohms yet is 3.7ohms, same as primary ? Can anyone explain why exactly same ? Do I need to unsolder connection on coil ?
Going to see if someone local can check coil performance before I replace I think.

take your point on strip down but its my first ......... so if I can avoid - and that bearing feels ok.

C12 part.




I don't think the coil is original as it is marked 'Made in W. Germany'. I'm sure the engine it came off didn't have a spark but the coil is untested.

You're welcome to it for price of the postage if it's of use to you.

If the coil is duff and you can't find a replacement you could try the 'transfer coil' trick

https://ukengineforum.forumotion.com/t6186-more-ignition-experiments

Hi Mattblack,
That is great, looks like mine apart from points housing and certainly worth a try.
I think I can pay for postage direct if you have a Hermes collection point nearby (in a corner shop or whatever). All you would have to do is print the label at the shop. If that works for you, I'll do that.
many thanks, Steve
Hi Woodsman -interesting mid, I'll bear that in mind if I can't replace. thanks

Steve A wrote:
Hi Woodsman -interesting mid, I'll bear that in mind if I can't replace.  thanks

Had a rummage in the spares box and have a mounting plate with clean yoke (?) and also coil (not villiers) which tests OK and could, with a bit of filing, be made to fit.  See how you get on with Matts and PM me if you have no luck.

I am happy be corrected but I think the chances of find a good pukkah coil are a little slim.

Success !
After a swap around and a partial rebuild, Matt's coil did the trick. Good spark with the correct gap. It fired up after a few pulls. I only let it run for a few seconds as the housing was off - I guess it could overheat without it. Got to put it together properly now and then start my refurb.
I haven't checked the timing yet - just put the flywheel back roughly in same position.
Thanks Matt, certainly proved worth trying and seeing it finally fire up is a big lift - maybe I still have a magic touch ! Thanks all for your input , I'll keep you posted on my 1st refurb- fingers crossed.
Still not sure on mark though -is that flywheel number not a clue ? I'll just use the Mk10/12 manual.

Excellent news.  
Please keep us posted with progress.

Steve A wrote:Success !
After a swap around and a partial rebuild, Matt's coil did the trick. Good spark with the correct gap. It fired up after a few pulls. I only let it run for a few seconds as the housing was off - I guess it could overheat without it. Got to put it together properly now and then start my refurb.
I haven't checked the timing yet - just put the flywheel back roughly in same position.
Thanks Matt, certainly proved worth trying and seeing it finally fire up is a big lift - maybe I still have a magic touch !  Thanks all for your input , I'll keep you posted on my 1st refurb- fingers crossed.
Still not sure on mark though -is that flywheel number not a clue ? I'll just use the Mk10/12 manual.

Glad it worked out for you!

Re: the mark, is there no serial/instruction plate on the cowling? The C12 has a different crankcase with the oil filler plug in it, but AFAIK the internals are the same.