M18 no spark.

redduece07 · #1 03-03-2019, 04:17 PM

I have the engine out of my 1882 to track an oil leak and troubleshoot a problem I had all last mowing season. The oil sending unit seemed to be the source of the oil but the other problem has me stumped. The engine will quit and sometimes it would start right back up, and other times it would have to sit for an hour or more. Sometimes it would miss really bad and may not quit, but clear up. So far I have replaced the ignition switch (because it was in poor shape), cleaned the connections, and checked and rechecked all electrical components. Now I believe it is the magneto. I have the motor on my bench and have ordered an ebay magneto (actually have two because I thought the first one may be defective) plus the original. My question is this: With the engine on the bench should I get spark if the magneto is good by cranking the engine with a battery? The gaping is set to .010 and one plug still in the head with the wire attached and the other being used to check for spark. The kill wire removed. I have tried all three magneto and no spark. Am I doing something wrong?

cooperino · #2 03-03-2019, 04:40 PM

The wire that connects to the mag gets grounded when you turn the key to off position. That wire needs to be open or not grounded for mag to make spark.
3 faulty mags? Possible but not probable.

ol'George · #3 03-03-2019, 05:49 PM

Do both plugs fire when laying on the head/block/metal ground?
They both should, while cranking over on the bench or in the equipment.
As Coop mentioned, the small ground wire is the magneto kill wire.
Also, some engines have a low oil pressure shutdown switch that screws in the side of the block, by the dipstick, and they will kill the magneto if low/no oil pressure occurs.
When testing make sure the kill wire is not hooked to the magneto.

cooperino · #4 03-03-2019, 06:09 PM

Just noticed you said kill wire removed. Maybe timing. Hows the keyway on flywheel?

redduece07 · #5 03-03-2019, 10:34 PM

I wouldn't think timing would affect the presence of the spark. I have checked both plugs for spark, being sure that the one not being checked is screwed in the head and still nothing. Put simply, if the magnet in the flywheel passes by the magneto (and the magneto is good and the kill wire removed) it should send spark to the plug. Correct?

ol'George · #6 03-03-2019, 10:44 PM

FWIW: the timing is not adjustable on the Mag 18, although the older KT's have points so there is some adjustment using point gap variation.
While checking flywheel key's is always a good thing, Mag.18's rarely have that problem, but I would look at the magnets on the underside of the flywheel, as frequently because of the ageing now, the attaching glue tends to loosen which can and does cause CHARGING problems.( but not spark)

ol'George · #7 03-03-2019, 10:46 PM

Quote:

Originally Posted by redduece07

I wouldn't think timing would affect the presence of the spark. I have checked both plugs for spark, being sure that the one not being checked is screwed in the head and still nothing. Put simply, if the magnet in the flywheel passes by the magneto (and the magneto is good and the kill wire removed) it should send spark to the plug. Correct?

Yes that is correct.

redduece07 · #8 03-03-2019, 10:56 PM

Thanks George. That is what I needed to hear. I m just having a hard time wrapping my mind around having 3 magnetos that are bad with 2 of them being new. I guess they don't make Chinese knock off parts like they used to! Anyone ever try the Oregon brand magnetos? I can get one of those for half the price of a Kohler.

CubDieselFan · #9 03-03-2019, 11:02 PM

The best I can remember most have not had to good of luck with the Chinese ones. They are a lot of trouble to replace so it might be best to stick to OEM.

ol'George · #10 03-03-2019, 11:08 PM

Quote:

Originally Posted by redduece07

Thanks George. That is what I needed to hear. I m just having a hard time wrapping my mind around having 3 magnetos that are bad with 2 of them being new. I guess they don't make Chinese knock off parts like they used to! Anyone ever try the Oregon brand magnetos? I can get one of those for half the price of a Kohler.

Had a member here with a "missing" condition,
after a complete engine overhaul to no avail, he found one plug wire inserted in the
new coil had excessive epoxy in the hole and it insulated it from making contact.
I personally, have an inexpensive aftermarket ebay coil that works well in the warm season, but lower than freezing temps, I just can't spin it fast enough to produce spark.
Lucky I don't use it but to mow in summer, my other 782 with cab does snow duty and will start in much lower temps.(OEM original coil)
one day I will change it out and use it for target practice, so I'm not tempted to keep it "just incase"