Magneto Questions

How hot should a Mag spark be ? As in how far a gap should it leap, color, etc. Does the impulse actually increase spark strength ? If so, how ? Can an impulse mechanism short the spark causing no start, but will start when spun faster like when tractor is pulled ? Talking about an E4A (Regular) Thanks, trying to learn something here ! Mine is working ok at this time...

15000 volts or more, 1/2 inch jump should be no issue.
Impulse coupling makes it possible to provide spark at near zero engine speed while hand cranking.
It operates up to normal electric starter speeds to provide enough rotor speed (magnet) to energize the coil primary such that the points and condenser system can collapse the secondary magnetism making spark. The system only works at less than Idle speeds. The system also effectively (on some Mags) retards the spark preventing kickback.
The mag usually (and all IH mags that I know of)has no centrifugal advance, and as such goes to full advance as soon as the impulse is out of the picture. Jim

And thats why you can start a mag. tractor with hardly even turning the crank. as my W12 once you stop it just pull on the crank very slow and as soon as the impuse trips its running.only 1/4 turn on the crank.

And thats why you can start a mag. tractor with hardly even turning the crank. as my W12 once you stop it just pull on the crank very slow and as soon as the impuse trips its running.only 1/4 turn on the crank.

How hot should a Mag spark be ?

Id say it should jump a 3/16 gap in free air thats still relatively blue in color and maybe up to an inch albeit then a thin wimpy yellow lookin spark

As in how far a gap should it leap, color, etc.

See above


Does the impulse actually increase spark strength ? If so, how ?

YES because the faster the magnetic rotor passes by the mags coil the more energy. At extreme slowwwwwwwww speed like hand cranking theres hardly any energy produced and consequently not enough to produce a spark to fire the plugs HOWEVER the impulse assembly allows a spring to wind up and then when its tripped it whirls the magnetic rotor fairly fast so a spark develops across the plug gap


Can an impulse mechanism short the spark causing no start, but will start when spun faster like when tractor is pulled

The impulse is a mechanical device that shouldnt short a spark, but when a tractor is pulled fast enough the rotor is spinning so fast the impulse isnt even working yet theres plenty spark energy to fire the plug. At RPM much over 250 the impulse assembly stops working altogether as theres no need then to increase the rotor speed UNLIKE at hand cranking speed when theres no spark unless the spring winds up n trips so the rotor spins fast enought to cause a spark

GET IT????????????????

John T

Yes ! I get it, thanks. So a bad impulse coupler could cause a hard or no start that pulling the tractor would cure, like if the spring was weak or broken, weak magnet, resistance somewhere,worn points, etc...Yes?
So when pull starting the tractor the impulse should be set to off?

On a regular a half inch of spark would jump the safety inside the mag, your looking for 1/4" of bright blue spark. Time to disassemble the impulse and clean all the rust and crud from inside it. Watch the spring (its kinda like working on a lawnmower pull start). If the spring is broken it usually won't work at all, if its clean and lubed with light oil it should work.

No need to engage the impulse if your pulling it.

These tractors start easy, if the carb and mag are good they start better than electric start ones. If the motors shot nothing will help.

You should consider sending that mag to someone like Nebraska Kirk for a rebuild and eliminate the question if its the mag or not

If you have weak spark you probably need a new coil in the mag. Another thing to cause weak spark is weak magnets. Hal

YES AGAIN WEEDHOPPER,,,,,,,,You're gettin it. If the spring was weak or broke or the impulse wasnt working at all, its still possible to pull start the tractor because at those faster engine speeds, theres plenty of spark and the impulse shouldnt be working anyway much over 250 RPM..If theres any manual impulse shut off??? Id use it for pull starts

HOWEVER worn points or carboned or burned or a weak condesnor etc makes for a weak spark REGARDLESS if under impulse or straight running

NOTE I AM NOTTTTTTTTT AN IHC MAG MAN THIS IS THEORY BUT DONT ASK ME MUCH MORE LOL I give Seminars on Wico C and X Mags at National John Deere shows but I dont know beans about those IH4 or whatever number mags other then the pure theory above.............

John T

My tractor runs really well so I am not expecting much is wrong, only occasionally I can t fire it up by hand crank, but always pull starts. Was wondering if impulse could be trouble, but Mag is still good. Seems possible now that I know how it works. Who is the Mag guy you mentioned ? Thanks !