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marval trouble

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Post by Diddy Thu Dec 06 2012, 00:52

when i got the engine it run well.but a crap paint job.so i took it all apart cleaned as we all or most of us do.put back to tegther now iv got no spark & the points dont seem to open the flywheel is turned.now the strang thing is its had a car coil fitted.after rebuild no spark so changed the coil for another but still no go.does any one know much about thease little engines.any help i would be greatfull.i got a little booklet from kelsey publishing but dont give much info eather.

dave
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Post by kevjhnsn Thu Dec 06 2012, 12:53

has the little backerlite end snapped off the crank /cam end of the lever arm ,have you tryed the screw for the points gap setting as if it was loose before rebuild it may of been disturbed and and set them to closed
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Post by PetterM Thu Dec 06 2012, 13:25

at the end of the day an engine is an engine.they all work on largly the same principels so there isnt much too go rong.if it was worken fine in tha ferst place it must be summfin u did so id suggest u retrace ur steps.

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Post by Diddy Thu Dec 06 2012, 22:11

did not touch the points.just the coul under the base.but was just a nut & bolt & the live wire.
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Post by Guest Fri Dec 07 2012, 11:17

Dave it might be a good idea to find a starting point and work your way through the system. I'd check the points first, check for any wear then gap them and see if your getting a spark if not check your wiring, I think it could be the use of a battery and coil that's wrong somewhere.

Stu.

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Post by nutgone Fri Dec 07 2012, 12:41

Sounds to me like the points have come out of adjustment. You should always re-gap points when you re-build an engine or magneto, weather you touched them or not, as they invariably come out of adjustment.

I would also recommend taking the points out & giving them a good clean with some very fine wet & dry or a fine diamond file (notice the emphasis on the word "Fine" here, they are supposed to be a polished finish, both very slightly convex or domed, but only very slightly, but that's in an ideal world, just so long as they are clean will do & not too rough, so no files or rough sand paper).
Make sure there are no missing Bakelite insulating washers & make sure they are meeting nice & squarely.

Finally replace them & gap them to whatever they are supposed to be (I'm guessing .015" to .020", so long as there's a good gap & they meet when closed, it should work).

It's also worth mentioning where on the opening sequence they should be gapped. The gap should be at its' widest soon after opening, not necessarily half way round the cam. This can usually be seen on the cam itself. They should be gapped at their widest point. But like I say, as long as there is a reasonable gap & they close firmly when they should, it should work.

If you still have trouble with the spark then replace the condenser.

Have you tested your replacement car coil with a multimeter? Do you know it actually works? It might be a ballasted coil, I think it should be non-ballasted for these applications, but again, it should work at least enough to get it started (I did know all about ballasted coils, but I've forgotten now, after all these magnetos. Pretty sure it should be non-ballasted though).

I wish I was a little closer, I would come over & have a look with you. I would love a Mar-Vil set myself, but just can't afford one right now. They are lovely little engines, but Villiers magnetos always were fiddly buggers.

Maybe I should offer my services & say "Send it down here by courier & I'll have a look at it for you". People keep saying I should be fixing engines for others & I've certainly got the time on my hands.

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