Need H4 Mag. help

John Saeli · Jan 8, 2015

I have a Left Hand H-4 Mag, but cannot determine the Lag Angle. It is either a 15 or 35 degree. The number stamped on it is: H4556141 Y. Anybody know? Thanks.

Janicholson · Jan 8, 2015

Turn it in the direction of rotation. Mark where it trips the impulse with a marker. The distance in degrees it moves the tip of the rotor will be distributor lag. X2 for crank lac. Jim

Jim Becker · Jan 8, 2015

The drive parts should be stamped according to direction and lag angle, as described on pages 54 and 55 here:
http://www.cleancomputes.com/Cub/Bl...Magnetos/GSS-5035 Service Manual Magnetos.htm

Tom Fleming · Jan 9, 2015

Jim's post is spot on. A little more info. Any gas start diesel mag has a lag angle of 15 degrees. This applies to the F4 and the H4 mags regardless of rotation. So, what is important here is to understand the application. Also, is just so happens that all the diesels are CCW rotation.

All the IHC letter series gassers were clockwise rotation except for the w9, I9 series, which is the 335 CID engines. There may be others that I am not aware of, but I know those ones for sure.

Hope this helps as well.

John Saeli · Jan 9, 2015

Thank you for the responses. The question is whether this Mag will work correctly on a T9 which is CCW. What is the correct Lag Angle required for the T9, W9 & I9? How important is the Lag Angle?

Owen Aaland · Jan 9, 2015

You need a 35° lag angle. If you install a diesel magneto with a 15° lag angle your timing will be 20° late or if you time it to fire at 35° it will fire at 20° BTDC when you are trying to start the engine. That will seriously affect how the engine cranks and would be very dangerous to anyone trying to hand crank the engine.

John Saeli · Jan 9, 2015

I appreciate all the responses. I tried to determine the Lag Angle of this Mag the way Jim described, but I had no luck. The H4- number on this Mag ends in "Y", not the L D or X. Not knowing what it came off from, I'm still stumped.

tractorguy2 · Jan 9, 2015

I thought magnetos labeled with the "y" were for contenntial combine engines?

teddy52food · Jan 9, 2015

Put the lower flange in a vise & clamp a vise grips on a drive lug, then bring it up to where the impulse catches. then turn it slowly, watching the cup on the dog. You should be able to guess if it turns 10 or 35 degrees before it trips.

John Saeli · Jan 10, 2015

Just did that, several times, & I come up with 65 degrees.

teddy52food · Jan 10, 2015

That would be a lot closer to 35 than to 10. I don't think there ever was a 65* retard.

John Saeli · Jan 10, 2015

I'm doing something wrong.

Need H4 Mag. help

John Saeli

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Janicholson

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Jim Becker

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Tom Fleming

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John Saeli

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Owen Aaland

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John Saeli

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tractorguy2

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teddy52food

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John Saeli

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teddy52food

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John Saeli

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