Mag Experts

James Williams · Aug 4, 2015

Im working on a Farmall F12 Waukesha,It is a 4 cylinder flat head motor and Im sure it times to TDC.It has a Fairbanks-Morse FMx41A mag on it,Which is auto advance.I am going to set it to trip at TDC.The question I have is will this mag retard itself or do I need to set it to snap a little after TDC?

jimmy

greenmech · Aug 4, 2015

You want the mag to trip the impulse at top dead center when starting. It will advance as the rpms rise. Ron Mn

mite-help · Aug 4, 2015

Think its called lag angle. the impulse spring winds up doing cranking, allowing the piston to travel beyond tdc to avoid kickback when it fires. it advances when impulse is disabled by rpm. there is a lot of different 'lag' settings. as long as you have proper match between engine/mag, be ok. waukasha engines that I used to work on used Am/bosch with a plate that could be moved to adjust that degree of delay. anyhow, find proper timing setting-[ tdc-5*before, etc ] set mag to fire @ that point, impulse delay will be what it is.

James Williams · Aug 4, 2015

Ive got the mag set to click just as the crankshaft just starts to roll to start the piston down

jimmy

teddy52food · Aug 4, 2015

Set it to snap at TDC or a degree or 2 after. The spark will advance when it speeds up & the impulse stays out.

JRSutton · Aug 4, 2015

Slightly after tdc. You shouldn't go too far past, just enough to be sure you are past, don't worry about a number.

There's no good reason to try to get it exactly at tdc, but many people seem to want to try.

Those are the people that have never felt a kickback while hand starting.

Mag Experts

James Williams

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greenmech

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mite-help

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James Williams

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teddy52food

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JRSutton

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