I have a BTH type M1 - B2 Magneto that is fitted to my Ruston APR.
The magneto produces a good spark when spun by hand but when fitted to the
engine I cannot turn the engine over fast enough to get a spark. I am
turning the engine with the inlet valve open so no compression. I've also
tried a few different good sparkplugs but still no spark.
Is there anything I can do to get a spark form the magneto at slower
speeds? even something temporary just to get the engine started would do.
I'm not sure what quick fixes will do for you except put off the evil day when
the magneto is reconditioned. A good mag
makes owning an old engine so much more pleasant.
I trust you've cleaned the points and made sure the gap is correct and they are
opening at the right point.
Check the coil resistances if you have access to a multimeter, most duff mags
I've owned have been open circuit in the
HT section. A mag coil has three connections normally, common (connected to the
body of the mag), LT (connected to the
points) and HT (connected to the sparkplug). You should get a very small number
of Ohms between the LT and common, and
somewhere in the region of 10-20 kilohms between the HT connection and common.
If, as is often the case, the reading
on the HT section is Megohms, then you need a coil rewind. You *can* get a
spark out of such a coil, as the HT current
can jump the gap in the coil, but the intensity of the spark will be much less,
particularly at low speed. This will
mean troublesome or no starting, and will make you hate your engine and result
in the dog having spanners thrown at it
engine I cannot turn the engine over fast
compression. I've also tried a few
even something temporary just to get the
It may also be as simple as a bad circuit through the engine, make sure you
have metal to metal contact between the Mag and the engine and make sure the
female and male plug threads are clean also.
Arthur G wrote:
If the points are really clean & dry, then this sounds to me like a lack of
magnetism. Arthur is right, poor or unreliable starting will foul your
relationship with your engine, so hoik it off & get it fixed!
There ought to be a way of fitting coil ignition temporarily utilising the
points in the magneto, but I'm not smart enough to figure that out - bet you
others here are tho' ;o))
J. Kim Siddorn,
I wonder? It is just possible that the magneto base plate is not making good
contact with the engine. Just as an experiment, Liam, trap a wire under one
of the magneto case screws & wrap the other end directly around the plug
Worth a try ..............
J. Kim Siddorn,
I've checked and cleaned the points and everything else for that mater.
I've stripped it down and checked the coil resistances. Common to LT is 0.9
Ohms and common to HT is 2.8k Ohms, Does that sound OK?
Also tried moving the cam to different positions but the strongest spark is
where it was set anyway and tried a bit of wire between magneto case and
plug to check its earthing properly.
I have just repaired two Wico EK mags using parts from a company called
`Standard Magneto Company` in Chicago, USA. They do a full repair kit for
these and other magnetos. The delivery was fast and every email was answered
promptly. I would like to see anyone get a two full repair kits (Coils,
leadout, points, cables, insulation etc) for the princely sum of £76
delivered in this country!!!!
I now have two EK`s that will blow your socks off.
Might be worth a try for a coil etc for your mag.
P.S. They also take payment via paypal, which is a great help.
I know nothing about magnetos but had to convert my miller roughneck
welder with kohler engine to run on battery and coil. Simple enough to
do, first remove wire from magneto to contact breaker, take positive
lead from battery to + on coil, - on coil to insulated side of points
and ground battery - to engine. Remember to disconnect battery after
A work mate did it to his sons vintage lawn mower, he used a mains 240v to
12vdc power supply and a car coil. all you would need is to hide the 12v car
battery and wire it like a car / bike ignition.
John Manders wrote: