Landmaster Gardenmaster 80 problem

[Paul Waites]

Hi all,

No usually a "stationary" engine but hopefully someone will be able to
guide me:

I've got an ancient "Gardenmaster 80" cultivator made by Landmaster in
the 1950's. It has been a good friend down the allotment saving a lot of
backache.

This year it won't start! I spin the flywheel and can get a nice
electric shock if I stick my finger in the plug lead but will it as heck
spark a spark plug. I therefore think the magneto has not enough magnetism.

Any theories welcome:
a) Specialists in JAP engines (model s80 type 24 two stroke).
b) Anyone got a manual
c) Any ideas how to get the flywheel off and take a look at the ignition.

It seems a shame to scrap the thing (I don't like to throw anything out)
as it seems to have so much more umph than my fathers modern rotivator.

Cheers for any advice

Paul.

p.s. Here's a URL of one of the beasts:
http://www.nationaltractorshow.co.uk/cgi-bin/2003/gallery2003.cgi?img=0304

[Kim Siddorn]

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.

Post by Paul Waites
Hi all,
No usually a "stationary" engine but hopefully someone will be able to
I've got an ancient "Gardenmaster 80" cultivator made by Landmaster in
the 1950's. It has been a good friend down the allotment saving a lot of
backache.
This year it won't start! I spin the flywheel and can get a nice
electric shock if I stick my finger in the plug lead but will it as heck
spark a spark plug. I therefore think the magneto has not enough magnetism.
a) Specialists in JAP engines (model s80 type 24 two stroke).
b) Anyone got a manual
c) Any ideas how to get the flywheel off and take a look at the ignition.
It seems a shame to scrap the thing (I don't like to throw anything out)
as it seems to have so much more umph than my fathers modern rotivator.
Cheers for any advice
Paul.
http://www.nationaltractorshow.co.uk/cgi-bin/2003/gallery2003.cgi?img=0304

[Paul Waites]

Post by Kim Siddorn
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.

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

Paul.

[Colin Jacobs]

Got a manual & restored one. It is also a sod to start.

Post by Paul Waites

Post by Kim Siddorn
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.

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

[Campingstoveman]

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

[Kim Siddorn]

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.

--

regards,

Kim Siddorn.

Post by Campingstoveman
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

[Nick H]

http://www.britishonly.com/pdf/lucas/sectionD6.pdf

Might be of interest.

Loads of other good stuff on this site.

[Arthur G]

Well found, that man!

Very interesting and useful, thanks Nick.

Arthur G

Post by Nick H
http://www.britishonly.com/pdf/lucas/sectionD6.pdf
Might be of interest.
Loads of other good stuff on this site.
--
NHH

[Nick H]

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:-

Loading Image...

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 ;-)

[Arthur G]

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

Post by Nick H
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:-
http://www.magneto.co.uk/acatalog/985.jpg
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 ;-)
--
NHH

[Nick H]

Post by Arthur G
Nick,
at first glance it looks like a dipped ceramic, but *could* be a dipped

mica. To save me rooting through IIS's drawers

Post by Arthur G
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

Post by Arthur G
jpeg.

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

http://www.magneto.co.uk/acatalog/Index.html

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 ?)

[Arthur G]

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

Post by Arthur G

Post by Arthur G
Nick,
at first glance it looks like a dipped ceramic, but *could* be a dipped

mica. To save me rooting through IIS's drawers

Post by Arthur G
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

Post by Arthur G
jpeg.

I think he uses them as a generic replacement in a number of applications eg
Lucas 'N'
http://www.magneto.co.uk/acatalog/Index.html
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 ?)
--
NHH

[Nick H]

Post by Arthur G
In my experience, a megger is a good way to sh*g capacitors, and is

unsuitable for testing them. Most customer wrecked

Post by Arthur G
capacitors turn out to have been checked by some bright spark (literally) on a megger!

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 ;-)

[Prepair Ltd]

Post by Arthur G

Post by Arthur G
In my experience, a megger is a good way to sh*g capacitors, and is

unsuitable for testing them. Most customer wrecked

Post by Arthur G
capacitors turn out to have been checked by some bright spark (literally)

on a megger!
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 ;-)

Most meggers are AC output unless you opt for DC on one of the
duel-voltage types.

AC into a capacitor is NOT a good thing to do, and as Arthur says, the
cap is a short circuit at rest and discharged, so the sudden
application of 500V DC or AC tends to produce a high initial charging
current.

The cap looks like a standard multi-layer ceramic, but they don't go
high enough on volts, so a polyprop or polyester of one of that family
would be next on the list. ID'ing from a picture can be a problem...

For a magneto primary circuit you would have a few hundred volts of
back emf as the points open, so it would need to be AC rated at 350V
or so, that would narrow down the availability of components.

X-rated mains suppression cap's would be a good choice, but tend to be
bulky.

Peter
--
Peter A Forbes
Prepair Ltd, Luton, UK
***@easynet.co.uk
http://www.prepair.co.uk

[Nick H]

Post by Prepair Ltd
Most meggers are AC output unless you opt for DC on one of the
duel-voltage types.

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.

[Arthur G]

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

Arthur G

Post by Arthur G

Post by Arthur G
In my experience, a megger is a good way to sh*g capacitors, and is

unsuitable for testing them. Most customer wrecked

Post by Arthur G
capacitors turn out to have been checked by some bright spark (literally)

on a megger!
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 ;-)
--
NHH

[Nick H]

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

Actually you'd be spoilt something rotten!

[Campingstoveman]

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

Martin P

Post by Nick H

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

Actually you'd be spoilt something rotten!