changed spring on Governor and now won't start

Hello,
I took off the governor on my 1940 Farmall A and changed the spring. Now the tractor will not start. The rotor is lining up and the magneto trips at TDC (according to the flywheel mark) It was running before I did this. I am getting spark in the proper order at each plug. Have the H4 Magneto off on the bench. All I did was adjust the teeth to match up according to the manual. Again the rotor is giving spark at each cylinder in the proper firing order. Can't understand it.

The engine turns over exactly like when the capacitor is grounded to kill the engine. This got me to thinking may be it is that. I tightened the brass nut when I changed the governor spring. I am getting connection to ground on the brass post which should be insulated. It is coming from the red wire on the coil, which seems to be getting it from the clip on the second picture. Shouldn't the capacitor be isolated from ground? This was an issue before I changed it.

What you are observing is "normal". One end of the coil primary is grounded though the clip you mention, and the other end connects to the points and condenser.

The coil primary winding has very low resistance, which appears as a "short" on all but the lowest Ohms setting on a quality meter.

Also, with everything connected back up, when the points are closed, they also shunt the condenser terminal to ground.

As to the timing, the flywheel timing mark lines up every revelation (obviously), but only every other revolution is the correct place for the mag to fire #1.

So it is possible you have the mag inserted in the drive slots 180? "off".

Also, did you verify the mag really WASN'T sparking before attempting to "fix" it?

It was running before I removed the governor. I think your 180 degree point is the lead I will follow. I fixed the H4 a few weeks ago and have done nothing to it other than take it off. :roll:

Oh, regarding the drive slot issue. How do I determine where the "R" should be when it trips?

As to the "R", where are you seeing that, do you have the cover over the rotor drive gears off?

Look at page 51 at the link below.

Also, all the "timing to engine" info is on there.

http://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html

Bob, i have the rotor lined up with the factory notched teeth. I have the rotor just before no 1 wire on the cap. I turned the engine to TDC on the button. I rotate the magneto outward and it trips with the rotor perfectly on number one. If I was out 180 it would be very obvious. The thing is, it worked until I removed the governor.

Check your linkage to the carb,maybe binding, and holding the throttle plate closed.

(quoted from post at 20:22:17 08/04/18) Bob, i have the rotor lined up with the factory notched teeth. I have the rotor just before no 1 wire on the cap. I turned the engine to TDC on the button. I rotate the magneto outward and it trips with the rotor perfectly on number one. If I was out 180 it would be very obvious. The thing is, it worked until I removed the governor.

Click to expand...

1. Have you verified that the mag is making spark? (Guess you've already answered that!)

2. (Once you've verified you have spark out of the mag.) You wrote "If I was out 180 it would be very obvious."

NO, actually it wouldn't be obvious. All the things you are ASSUMING to be correct will be the same whether the mag is 180º "off" or not.

If the mag is "off" 180º, when it trips at the TDC mark on the flywheel, it is firing (uselessly) at TDC at the end of the exhaust stroke, rather than TDC on the compression/firing stroke.

There's a couple of ways to figure this out... disable mag with kill switch you you don't get a shock from the removed spark plug wire and there's no chance of the engine starting, remove #1 sparkplug, and put a finger OVER (NOT in) the sparkplug hole while a helper slowly hand cranks the engine.

As the engine is coming up on the compression stroke, you will feel air being forced out of the cylinder. Stop at the TDC mark and install the mag.

If you were to crank it EXACTLY one more turn, it would be on TDC at the end of the exhaust stroke, which is where I SUSPECT you have it timed to now. From that point, cranking it exactly one more turn will get you back where you need to be.

The other way to verify the correct TDC is to remove the valve cover.

On the correct TDC, both valves in the #1 cylinder should have clearance between the valve and rockerarm, and the #4 cylinder's valves will be at "rollover", exhaust valve closing and intake valve opening.

On the WRONG TDC, the #1 cylinder valves will be at "rollover", and the #4 valves will be closed with play between the valves and rockerarms.


SO, if you've verified you have spark out of the mag, the next thing you have to do is verify it's firing on the correct. TDC.

NOTE... I'm NOT sure which type of rotor shaft you have (old style or new style) but if it's actually sparking out of all four high-tension terminals in order, the rotor apparently IS timed to the mag correctly.)

I will do this this morning, It has to be the problem, I changed nothing else other than setting the throttle linkage by the book and putting in a missing bearing on the governor shaft. I should have phrased it as a question not a statement with regards to the 180 being obvious. I meant from the perspective of the rotor. I did this whole procedure a few weeks ago and you used your exact instructions. You responded to my post then and now. Thanks!

Quick question. Should the rotor tab be exactly on the #1 post before it trips or land there after. I reset the gears to the manual and they are at the post before trip and past it after.

I wasn't on the compression TDC. I fixed it but haven't started the engine yet because wife is screaming at me to come in.

Rotor is a bit ahead of the high-tension terminal as the impulse is winding up, quickly passes it just as spark occurs.

GREAT news you found the trouble, HOPE all is well and it starts for you when you get the wife satisfied!

Wife says I am always having trouble with that "stupid machine" LOL. I only have it a month! Trouble is fun in this case.
Just wanted to thank you! Couldn't wrap my head around the mark going by the indicator twice. It is running very well now. 36 degrees BTDC and with the new Governor spring at 1540 rpm WOT. Seems to idle smoother at 625 than at the recommened 525. Not sure the screw is touching the spring arm inside the governor which concerns me as to when the spring stretches will the RPMs pick up?. Amazing how the design puts you at the perfect RPM with the weights. May be it is a fluke.