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J4 Magneto Timing - and More

E

equeen

Member
Attached photo is NOT of the engine I'm working with at the moment. However, I'm interested in the proper position of the slots/notches in the timing gear as viewed in this photo.

Crankshaft pulley of current engine is clearly notched for TDC on piston 1. About 11/16 of an inch BEFORE the TDC notch is another notch - for something I suppose. TDC viewed from plug hole clearly matches TDC notch on crankshaft pulley.

Question: When viewing C60 engine as in photo, with planned mag ignition; what should be the position of the slots in the timing unit?

Thanks.
a87296.jpg
 
The additonal notch is 16 degrees advance. You can ignore it with a magneto. 16 is full advance in the Cub battery ignition. The slots in your picture look about right for TDC. They should be 35 degrees above horizontal.
 
What tractor are you messing with is it also a Cub?? You can also use the TDC way as in get #1 piston up at TDC then line up the rotor on the mag so when installed it sits close to where it would fire and that gets you in the ball park so once running you can fine tune it. I use that way when people make the mistake of pulling the distributor out of things and then forget it has to go back in just so or it will not work. You do not know how many people will pull a distributor then move the engine and then find out timing the distributor is a key factor to a running engine
 
Yep, it's another cub that I'm tinkering with.

And, yes, I mess with things without considering the consequences at times. Of course I also learn that way.

Now, another stupid question. The mag is back on the bench with plugs. If I remove the rotor, then rotate the rotor 45 degrees or so, then re-install it without touching the lug end of the mag will I create a timing problem within the mag itself - if there is such a thing?

Stated another way, does the mag, itself - separate and apart from the engine combustion timing concern - have to be "timed", or whatever, to get the rotor in sync with the drive end of the mag?

Thanks.
 
I'll ask a question before answering yours. Is that a Fairbanks Morse J-4 mag or the IH mag??? If it is the Fairbanks mag J-4 send me an e-mail and I can make it easy on you because I have the manual for that mag on the computer so I can then send you that manual which tells you how to time it and all that neat stuff. Been to many years since I have been in a mag other then to clean the points and on that mag you can not mess up but then that is on a 2 cylinder engine
 
It's the IH Mag.

Here's a paragraph from the Cub Operators Manual:
"With the engine on the top dead center of the No. 1 firing stroke, turn the distributor rotor until end "B" of the distributor rotor arm points to the No. 1 terminal on the distributor cap. Place the distributor body on the magneto and be sure the rotor shaft enters the D-shaped hole in the magneto rotor pinion."

Huh? Place what distributor "body" on the mag?
 
Why don't you bring No1 piston near the radiator to TDC on the compression stroke? Then rotate the rotor so it points to the No1 plug tower which is about 1 0'clock and install the mag. Your firing order is: Hal

2-1
4-3 As the rotor rotates CW.
 
Hal, your thought makes perfect sense to me. Not that it should matter, but on this IH Mag, the #1 plug tower is dead on 12 o'clock.

Are there any governor or other issues that would arise if I made this change?

I'm getting ready to bolt her back on.
 
Since you removed the timing gear did you reinstall it correctly. Here's how the timing marks on the Cub should be. Hal
a87323.jpg
 
I'm not a politician, but perhaps "I mis-spoke". And, perhaps I'm still in a world of hurt.

Fig IH329 showing the timing gear train for the Cub......
I did not remove the front cover of the engine block, thus did not remove either of the 3 gears.

I did remove the complete "governor" assembly, thus the magneto drive gear which meshes with the large left gear of the "timing gear train".

Problem/no problem?
 
If it is like the H4 mag, there are 2 gears in that housing you take off to get to the points. 2 screws on that little plate. Small gear has 2 teeth edge ground off. those have to match the C on the big gear.
 
I give up - for now.

New points and condenser, but no change. Hits one time on a plug, then nothing else. Nice blue fire all the time from coil.

Removed side post and cleaned/inspected insulator. No problem. Re-installed. Hit one time on a plug, then nothing else. Still fires the coil.

Sooooooo, it stays on/near the bench until I put it away or try again sometime. Have a distributor coming anyway.

As to the governor and timing of the mag drive gear. I was able to see the two punch marks on the idler gear without removing the front plate of the engine. Using the photo from the IH Manual and counting teeth I believe that I've positioned the magneto-governor drive gear very close to correct. I suppose I'll find out after I get the distributor in and installed.

Thanks to all for your help today!
 
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