magneto

[old_bartender]

i am working on a 1970 rt1 360 yamaha. i got a voltage from the magneto to the ignition coil .but i get no spark out of a good spark plug. ok might have a bad coil my manual has a value of 0.6 ohm for the primary and 5.8 for the secondary. the sec side seem low to me compaired to other coil i have for battery ignition. the ignition used 5k ohm plug cap. ty for all the help.

[Dragonrider]

Boy...it's been a long time on magnetos for me...I had a Honda 350 with those suckers...

I remember the points were particularly critical (As well as the clearance on the magnetos) as the points HAVE to break just before the voltage starts to fall from the magneto. Exactly just before...

If they break early, the coil is not charged enough, and if they break even a little late (the voltage starting to fall from the magneto) it affects the wave-form of the coil field collapse and it won't produce enough voltage to spark.

And if the clearance is not right on the magnetos, there is not enough voltage in the first place...

Picky, picky, picky!

I remember sitting beside the highway...in the hail and rain, with my leather jacket over my head and the magneto cover while trying to adjust all that stuff (with a flashlight in my mouth and sitting in cold rain water of course...)

I finally put an o-scope on mine and found that the timing of the magneto discharge was a little out with the point's breaking when everything was set to spec. Had to come up with my own spec...and it was different on a different (friend's) bike.

Best of luck, and check (recheck) all those settings/clearances.

Man, you've dredged up some memories...(and a cold sweat). I think I'll go kiss my electronic ignition box right now!

[DiverRay]

Most old magneto ignitions didn't like the resistor caps. Try putting on a non resistor cap, and non resistor plug. I remember the old Yamaha's used to cause everyone with an AM radio headaches. One check you can easily do is pull the plug, unscrew the cap off the wire, and hold the wire near a GOOD engine ground as you turn the engine over with the kick starter. It helps if you can get someone to kick it, as it needs to spin fairly fast to produce a spark.
Goos luck.
Ray