Landmaster Gardenmaster 80 problem

First off, go and get a nice NEW spark plug. New, you notice, not a good one you have tucked away. That alone might well be enough to get it going.

If not, drain the petrol out and put in a nice fresh gallon. Don't forget to drain the float bowl.

Still nothing? might well be the points, so you'll need to clean them. A slip of 800grit Wet & Dry paper moved in and out of the points should do it Wipe out residue with a clean cloth, then slide a bit of meths soaked card between the points to clean off what remains. Finish with dry card.

If it still doesn't respond, it might be poor compression - but magnetism does not leak away on its own & magnets were pretty good by the post war years.

regards,

Kim Siddorn.

Cheers,..... Yes I confess I haave been using second hand plugs.

Paul.

Kim, "but magnetism does not leak away on its own & magnets were pretty good by the post war years."

Whilst your source of knowledge always amazes me, if magnatism does not leak is somebody stealing mine bwcause I have had to get a couple of mags re magnetized in the past so where has it gone then.

Martin P

All I know about magnetos & magnets I've picked up from others, so I may be wrong about some of this.

Usually, people remove the armature without putting a keeper in place. Also, they don't turn the armature until the magnets are 90o out of phase with the pole pieces, so the field collapses strongly into the earth's field as the armature is removed.

Once the armature is out, the magnetism can indeed leak away. As I understand it, this is caused by the precession of the earth, a very slight wobble on its axis causing varying magnetic fields to pull this way and that at the fields in the body of the magneto.

There were great advances in permanent magnet alloys in the 1930's and especially in WW2 and if treated properly, their magnetism should never need "freshening".

Finally, if you are having a magneto remagnetized, you should obviously do it with the armature in place.

Might be of interest.

Loads of other good stuff on this site.

Well found, that man!

Very interesting and useful, thanks Nick.

Glad it is of use, had it in my favourites for a while. Now perhaps you can tell us all what type of capacitor this is:-

Independent Ignition sell them as replacements for magneto applications at £11-80 plus VAT . But I suspect if you can ID it, we could all buy a bag full for fourpence from RS ;-)

Nick, at first glance it looks like a dipped ceramic, but *could* be a dipped mica. To save me rooting through IIS's drawers more than I need to, could you tell me which magneto it's supplied as a spare for? The link just takes me to a small jpeg.

In general, from what I can gather, magneto capacitors (or condensers if you like) need to withstand be able to withstand 500VDC (though they're in the low tension circuit, they do see some back emf) and have a relatively high dv/dt capability. Martin Percy is a great fan of Evox Rifa, and I would certainly attest that they are the Rolls Royce of suppression capacitors. He is the man to whom I put all my queries to, and I've never stumped him yet.

I'm sure that IIS are charging plenty of mark-up oon these, as they seem to charge lots for everything they do.

What mag do you want to replace the condenser in?

If anyone here needs small numbers of capacitors/condensers tested, I'm happy to do it, though in my experience most old wound capacitors are knackered, while most micas are okay. Unless you've got kit to measure the insulation resistance at 500VDC you cannot usefully test a magneto capacitor yourself.

Regards, Arthur G

"Arthur G" wrote in (snip):-

mica. To save me rooting through IIS's drawers

spare for? The link just takes me to a small

I think he uses them as a generic replacement in a number of applications eg Lucas 'N'

Nothing particular in mind at the moment, just though that they might be something useful to have on the shelf.

BTW what sort of insulation resistance would you expect to see on a good cap? I can test with a Wee Megger (500V ?)

Nick,

IR (insulation resistance) pass mark for polyester is >10000 Megohms below a capacitance of 1uF. I must confess it's so long since I worked with paper capacitors (which most post war mags will have) I can't remember the figure, but I would guess about half this figure. Polypropylene's IR is five times higher than polyester.

In my experience, a megger is a good way to sh*g capacitors, and is unsuitable for testing them. Most customer wrecked capacitors turn out to have been checked by some bright spark (literally) on a megger!

To measure insulation resistance (which is the best quality check of the dielectric material) a stable voltage needs to be applied for a prolonged period of time while the capacitor charges. All capacitors are short circuit when a charge is first applied and eventually when fully charged, draw no charging current, the only current flowing is a tiny leakage current determined by the IR. If the voltage isn't absolutely stable, then the capacitor will fluctuate in voltage, either sinking or sourcing current accordingly. This will prevent any meaningful reading of IR, which determines (if the capacitor's good) tiny leakage current flowing when the capacitor is charged to an unchanging voltage.

HTH

Arthur G

"Arthur G" wrote (snip):-

unsuitable for testing them. Most customer wrecked

Thanks for that. I must admit it hadn't occurred to me that the lumpy old volts produced by yours truly winding away furiously at the handle could actually be damaging - I'll stick to using it to electrocute the cat ;-)

I hope I don't come back in a future life as a cat in the Highfield residence! ;-)

Arthur G

"Arthur G" wrote:-

Actually you'd be spoilt something rotten!

"Prepair Ltd" wrote (snip):-

Thought there was a comm on the genny so giving lumpy DC. Though, now Arthur has mentioned it, I appreciate that the AC componant (lumps) could still damage a cat - sorry cap.

"Spoilt" is an unfortunate word if your a cat :-))

Mart> "Arthur G" wrote:-