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Magneto on A update

grandpa Love

grandpa Love

Well-known Member
4 hours in the barn.....new wires (copper core) new plugs,new distributor cap,and new rotor. Whole lot of nothing. Remove coil wire from cap and spark jumps almost an inch to the block. But no fire to the plugs. Had 3 rotors so my wife filed one a bit and bent the metal strip down a bit and we had fire from all 4 plugs. Tried to fire it up and got a couple terrible back fires out the exhaust pipe! LOUD!!! Tinkered with the mag timing and made things worse. Now no fire to the plugs again, but great spark from coil wire........oh well, gotta work tomorrow. Will try again on Thursday. Any thoughts welcome.. .
 
Gene bender, we think so.....but to be sure we are planning on taking off valve cover...other wise how do you know? Air pushes finger off on compression and exhaust?
 
What kind of plugs are they? Be sure they are non-resistor. I use autolite 3116.
With the magneto off the tractor and held in a vise, you should be able to rotate it by hand (either direction) and throw 1/4 inch sparks from the center wire. Sounds like you have this. Then it is a matter of getting spark to the plugs. JANicholson's comment on the timing gears is what comes to mind. Do an internet search for the "wrenching with rachel" video on mag rebuilds. It's pretty good, and will show how to time to these gears. I am pretty sure yours should be "right timed." (not left).
 
Under the rotor there are 2 screws & a cap to take off. Clean the grease off the little gear to find the odd tooth. That has to line up with the C on the big gear.
 
The two gears (behind the metal plate, under the rotor) have timing marks, one is a clipped tooth, and the other is a mark. (IIRC) they must be aligned for correct timing. The rotor will look like it is off, but that is because of the offset of the impuls coupling. Jim
 
Depending on the year, the one gear will have a "R" or "L" stamped on it. I think you want the "R" lined up with the clipped tooth.

From the GSS-5035 service manual: "The old distributor gear has two markings: (1) counterclockwise rotation --two teeth cut off at an angle, (2) clockwise rotation--two teeth with ends partially cut away by a circular cutter. When assembling this type distributor gear to the pinion, set the two marked teeth straddle of the one marked tooth on the rotor gear pinion. The old distributor gear removed from the magneto will have but one set of markings on the gear, so there will be no possibility of confusion.

A change has been made on the later type distributor spindle and gear, changing the timing marks. The letters "R" and "L" are formed on the spindle. (Illustration 106). The "R" marking on the new distributor spindle is the setting for the clockwise magnet, and the "L" marking on the end of the distributor is a correct lineup for counter-clockwise magnetos."

Per page 50 of this manual, you want the "clockwise" ("right") timed magneto.
cvphoto33353.png
(Image shows "left timed.")
 
MOST likely, you have "stabbed" the mag 180? "off" into the mag drive and the sparkplugs are firing on the exhaust stroke rather than at the end of the compression stroke. (Think BACKFIRE.)

I think I posted this link before for you, if not, here's a link to the official OH Blue Ribbon Service Manual for magnetos.

It will tell you how to time the rotor gears correctly, and how to time the mag correctly to the engine.

http://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html
 
THE push is much greater on compression unless the valves are needing attention. Remove all plugs hook up #1 and ground it so it fires. Now put your thumb over the #1 hole and turn engine over with sw on and watch if the plug fires when engine hits compression also if you remove the cap you can see if the rotor snaps at #1 position when it hits compression. Sounds like the mag is 180 off didn't you say #4 fires when #1 is on compression which would mean the mag is off 180 just remove the mag turn 1/2 turn and re install. If I was there is could solve the problem in 2 minutes. I have 6 mags and they just work fine.
 
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