Magneto speed

Hi,
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.
Thanks
Liam
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Reply to
Liam
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Liam,
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 :-).
Regards, Arthur G
engine I cannot turn the engine over fast
compression. I've also tried a few
even something temporary just to get the
Reply to
Arthur G
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.
Martin P
Arthur G wrote:
Reply to
Campingstoveman
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))
Regards,
J. Kim Siddorn,
Reply to
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 body.
Worth a try ..............
Regards,
J. Kim Siddorn,
Reply to
Kim Siddorn
Hi 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.
Thanks
Liam
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Reply to
Liam
The HT is about half the minimum for a passable BTH. On that basis a rewind is in order. hth Roland
Reply to
Roland Craven
Any recommendations on who to contact for a rewind. Is there anyone in the North East area who does them?
Thanks
Liam
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Reply to
Liam
I've never done it but there are a lot of Morgan V twins running around with non-functioning mags and a pair of HT coils.
John
Reply to
John Manders
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.
Cheers, MartinH
P.S. They also take payment via paypal, which is a great help.
particularly
Reply to
martin hirst
Link here in case anyone wants to keep it for the future.
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Cheers, MartinH
Reply to
martin hirst
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 use.
AJH
Reply to
AJH
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.
Martin P
John Manders wrote:
Reply to
Campingstoveman
I can't see a Yank supplier doing coils for a Brit mag, but could be wrong.
Martin Percy is my first choice for mag work (see SEM helpline) or if you're in a hurry try
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are based in Stoud and come recommended to me by two whose judgement I trust, though I've never used their services myself.
HTH
Regards, Arthur G
Reply to
Arthur G

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