RTS Magneto

fordfx413 · Feb 22, 2020

I have a RTS tractor. I can not get a spark. I looks like someone had recently replaced the points, condenser and maybe the coil at one time. Anyway to test the magneto to find out which part is bad? Best place to find parts? Thanks

Bob · Feb 22, 2020

(quoted from post at 22:22:01 02/22/20) I have a RTS tractor. I can not get a spark. I looks like someone had recently replaced the points, condenser and maybe the coil at one time. Anyway to test the magneto to find out which part is bad? Best place to find parts? Thanks

What is the make and model of the MAGNETO?

Once that is known it's quite likely that a factory service manual for it can be found on-line.

That being said, the MOST likely cause of "no spark" with anything with breaker points is a non-conductive film, or light corrosion on the points.

To clean the points, burnish them by drawing a strip of clean white "cardstock" through them repeatedly, then (with points open), clean any "dust" and residue off of them with electrical contact cleaner and allow them to "air dry" before checking for spark.

If that doesn't help, look for something that's shorting to ground, in the coil-points/condenser wiring, and at any insulators in that area for damage.

Also, is the "impulse" working?

molinegb · Feb 23, 2020

All mags on R and Z U G used the FM 4Bk4. U and G had different impulse.

teddy52food · Feb 23, 2020

I do mags as a hobby. I have the testers to check it all out & have a charger for the magnet.

fordfx413 · Feb 23, 2020

I did a little more testing. I have ground to the terminal where the ignition switch hooks to all the time. With the points opened or closed. Is that normal? The wiring looks good, no rubs or nothing. This magneto is a fairbank-morse Type FM

Bob · Feb 23, 2020

(quoted from post at 17:23:15 02/23/20) I did a little more testing. I have ground to the terminal where the ignition switch hooks to all the time. With the points opened or closed. Is that normal? The wiring looks good, no rubs or nothing. This magneto is a fairbank-morse Type FM

When you are checking the resistance from the "kill" terminal to ground, if the points are "open", the coil primary is still shunted across the open points to ground, and you are measuring it's resistance, likely around 0.5 Ohms, so it appears as almost a dead short.

You mentioned "ignition switch", I hope this is a grounding "kill switch", and there's NO connection between the battery electrical system on the tractor and the ignition system!

molinegb · Feb 23, 2020

Remove wire and see if spark. Check resistance on wire should read infinity. Like Bob says terminal on mag will read low ohms as reading windings in coil. Is there a noticable click when cranking? Should hear if impulse working. A mag off a U or G will not work on a R or Z as impulse different.

fordfx413 · Feb 23, 2020

Bob, Sorry for the confusion... it is a ground switch.

Bob · Feb 24, 2020

(quoted from post at 20:30:06 02/23/20) Bob, Sorry for the confusion... it is a ground switch.

That's GOOD to hear.

I seen more than once where guys do not realize that a mag is "self-powered" and put battery current to them.

NOT pretty.

RTS Magneto

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