magneto cam off a few teeth?

sald

Member
I can't seem to get my static timing correct. I can't push the magneto any more toward the engine to get it to pulse at TDC. I is off by about 18 degrees after TDC. With a timing light I can't get more than 18 degrees. I understand I need to be at 35. So how to I get the other 17-18? Someone messed with the magneto rotor placement so who knows what was done. How do I go about reindexing the magneto-cam meshing?
 
Also, shouldn't I be pulling the magneto away not in? for the pulse. Someone told me to push it toward the engine but I would think I should pull. Either way I couldn't get it to pulse.
 
It would help if we knew which magneto/tractor you are working on. Most IH magnetos are retarded maximum when turned as far toward engine as they will go. Turn them away from engine to advance the spark.

The rotor gear will not affect when it trips, but will effect where spark is delivered. There is a mark on the side of the rotor opposite the arm that looks like a mold mark, which is actually a timing mark. That mark is matched with either a raised mark or notched tooth on the drive gear depending on which one is used.
 
Forgot to say, yes, you start with mag against the engine and timing mark at pointer and move mag away from engine to get it to trip. These instruction are valid for a gas powered tractor using a magneto. If you are working on a gas start diesel, the magneto turns in the opposite direction, but I assume the directions are still the same since it mounts on the left side of the engine.
 
Sorry about that, it is an H4 1940 Farmall A. The rotor alignment was mentioned because I think it was a sloppy fix to another problem. That is why I suspect the governor gear to be off by a tooth or two.
 
How do I go about reindexing the magneto-cam meshing?
he only way that I can see to do that is by removing the timing cover and checking the timing marks.

Does the front of engine appear to have been played with at a recent point in time? New gaskets, replacement bolt that may have been lost, improvised radiator cushions etc.
 
Make a mark on the body where the cap fits where #1 tower is. Now remove the cap and look where the rotor
is when #1 is on compression you need the rotor pointing there mite need to move the gears that drive the rotor
so the rotor is lined up there. If that doesent make the engine start the mag gear thats driven by the cam mite
be off you need to remove the front cover to see if the two dots on the cam gear are lined you with the two dots
on the mag gear. With a magneto those gears have to be in alignment or you just wont get the engine to start
cause the valves will be out of time with compression when the mag fires. With the dots lined up and mag
installed with rotor pointing at tower #1 those engines will start great providing carb is OK i have several A
andBs with mags they are trouble free and just do their job. If you want to call 319-430-3907 anytime
 
I cant confrm if the dots are lined up. I did have to re align the rotor because it was messed with. There is no way to see the marks by pulling the governor? Would one or two teeth prevent it from running?
 
Forgot to say... I would imagine that if the governor gear was off a few teeth it would affect the attitude of the angle of the magneto housing from plum. It may lean noticeably outward to compensate for the misalignment. Limited by the travel of the curved slot on the bottom stop bolt.
 
Oh, by the way, my Rotor Post doesn't have any marks...
mvphoto20483.png
 
Marks are on the other end. It won't matter as the spark occurs when it snaps. Take off the 2 screws & check it. Remove the governor housing & find the mark on the gear. Keep slowly turning & it should line up with the mark on the cam gear. If not pull it out enough to line it up. then try the mag before you put the housing back on. There are 2 marks on the cam gear. If not right on one, use the other.
 
I will try to shoot some pictures and post them. I have been searching for some and can't find any. Pictures are the key to understanding.
 
You are making this WAY more difficult than it is...


Once you verify the mag itself is set up properly, if spark timing is still "out of range" with the slotted/rotate the mag adjustment, you will then have to undo the governor and reset the governor shaft a tooth or several, as needed, forward or backwards.

The GSS-5035 manual explains how to time the mag to the engine and how to time the rotor gears. You have an older-style rotor shaft without the lettered "R" and "L" markings.

The markings on those are gear teeth (hidden under the two-screw cover in your picture) with a bevel or cut at the end of two teeth.

Even the breaker cam-to-main-shaft relationship can get screwed up, AGAIN covered in the GSS-5035.

Look at Pages 48 thru about 52.

<img src = "http://oi66.tinypic.com/2znssox.jpg">

Link to GSS-5035... copy and paste into browser address bar if other link doesn't work..

http://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html
GSS 5035
 
Ok, got the static timing perfect. Required thorough cleaning and lubricating the magneto. The only thing is, I had to pull the magneto pretty far away from the engine to get it to trip at TDC. At some point I may go in and re index the governor gear. I had plans to change the springs anyway.
Have you ever seen them leaning this far out. It is almost at the max if not already.
mvphoto20493.png
 
Thanks Bob,
I actually timed it once I got the trip correct. Not sure about the marks. I just saw your post after I finished.
 
Yeah I figured. Anyway, It is running well now. 36degrees BTDC on the timing light. Adjusted the governor up to 1520 on high idle. It was at 1400. Amazing the difference of how it ran up the hill with no problem.

Next, figure out why I can't get the 10si alternator to charge even after rebuilding it with a self exciting regulator. I think may be the stator at this point.

Then need to drop the pan because I had lightish brown oil with chunks of crud when I changed the oil. Have a feeling the screens are clogged on the pump and that is why I am sitting at the very end of the red on the oil pressure gauge.

Thanks for everyones help! :D :D :D :D :D
 
It is amazing how much better an engine runs with correct timing.

I can adjust the timing on my EFI, and can hear the difference.
 

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