Timing Question for Tom Fleming and Others on F-4 Magneto

[Barack]

I teach classes on distributors and magnetos and write articles on electrical topics. To my knowledge the F-4 is the only magneto with a manual spark advance lever. The H-4 and Wico mags don't have one.

As you said, the impulse cuts out at 200-300rpm. What is the timing then, with the manual lever retarded? Then, how much additional timing is there with the manual lever fully advanced?

With an H-4 you get running timing as soon as the impulse goes off. The F-4 is obviously different as there must be some advance when the tractor starts and the impulse goes off. Then, when the lever is advanced, there must be some more advance.

So far, this question for some reason has totally baffled all responders. My motive is simply to understand how the system works! I don't have an F-20 anymore, so I can't experiment.

Again, how much advance is there over crank timing with the impulse on, and running timing with the impulse off and the manual lever retarded? Then, how much additional advance with the manual lever fully advanced? Thanks

 

[robgIN]

Part of the reason you haven't gotten the response you want is apparently IH didn't publish that info or no one has found it yet. IH also didn't put timing scales on the crank pulleys of tractors back then either so it's not like someone can just go put a timing light on an F-20 and get your answer. The available tools in the 30s was very limited compared to today, manufacturers found what worked and built it. If you want to know this that bad you are going to have to invest some of your own time to get the answer it looks like. Lots of tractors with F4 mags out there, grab a light, make a degree scale for the pulley and get to it.

 

[Nebraska Cowman]

Here is a discussion we had on lag angle that may help
lag angle

 

[Nebraska Cowman]

Eisemann, Bosch, K-W, Splitdorf all made adjustable spark advance. So did the the IH E4 magneto. I would not think the lever would change it too far. Maybe + or - 10°? The actual timing would depend on the individual application and how it was adjusted on the tractor. Any parts wear or change in points adjustment would also effect timing slightly.

 

[Nebraska Cowman]

Here is a link to the index page. The manual is downloadable in sections.
magneto service

 

[rustred]

the answer to your last question is... there is no change in timing from manual cranking to engine started once impulse kicks out. i posted the rest in your last post below.

 

[Earl-IL]

Lets talk magneto's. Send me a email & the best time for me to call you.

Earl In Illinois

 

[Nebraska Cowman]

Kirk is absolutely correct in his reply to your earlier post. The more I think it through the clearer it becomes. Full retard on the lever is ZERO advance. The timing instruction in the book calls for TDC timing with the lever fully retarded.