Now- Cranky Cub won't start...

[Don McCombs]

Cables are all new.

Are they graphite or copper core?

I think these were battery cables, not spark plug.

[JustJim]

Friends-

Sure am grateful for all of the helpful suggestions!

This Cub is a little different from the usual case here of trying to get a long neglected tractor going. Instead, it's as new as I could make it from stem to stern. That's why it has been so cotton pickin' frustrating - a year of work and too much money spent, and now I can't get the rascal to fire up! It's really pretty funny!

Battery cables - new from TM Tractor
Plugs - new
Points and condenser - new
Plug wires - new copper from TM
Wiring harness - new, made by me
Carburetor - freshly rebuilt, and have also switched in a known good carb from my '59
Battery - one year old 6-volt from Napa and have also switched in a 12-volt for testing

I know I've got a good carburetor in place now. Magneto timing is spot on. Point and plug gap verified correct. Spark looks good - bright blue - although when I tried an old plug with the gap expanded to 3/16" as a test, the spark is yellow, but it will cover that huge gap. I'm running out of things to try, except perhaps a new coil.

Oh well, if it was easy I guess it wouldn't be fun!

[wrz]

Put a cork in number one spark plug hole and when it pops check to see if your wire from the distributor lines up to the rotor and the pointer is on the mark on the front pulley. (crank by hand) If it does not match the timing of the valves it will not fire.(180 degrees off)
Wm

[Pap]

Jim.... I am sorry that you are having a little bit of fun trying to get " Cranky " fired up.
I wish I could be there to help you friend.

[Rick Spivey]

Your earlier post said magneto, so I will assume you have a magneto with internal coil. If not, let us know what you have. I'm still thinking it's in the ignition system that you have a problem. I have worked on them for hours, swearing I had it all correct, only to find it 180 degrees out after all. So I suggest you triple check with an open mind all your timing. Double check pinion to rotor, and then double check magneto timing to TDC. Also, your spark plug wires should be copper core. And lastly check the distributor cap for cracks, or grayish traces inside, which might indicate the spark is leaking to ground. I know from experience that even when you are sure you got it all right, you will ultimately find it wrong....

[Greenthumbfarms]

Just my thoughts with my limited experience.
What method did you use for timing, static timing the Mag or did you use a light? Have you checked that the gears in the Mag are properly aligned with the two dots together?
When you set your float height did you make sure to use the gasket in your height measurement?
It may seem like a silly mistake but have you checked that all 4 plug wires are securely plugged in in both ends? Same with the coil-to-cap wire. Are you certain the plug wires are jn the correct order (1-3-4-2)? Go from the 12 o'clock position clockwise on the cap to check.
Have you tried disconnecting the kill switch wire on the Mag to see if that is causing it to ground out?

[Rick Spivey]

It just occurred to me that you said this was a rebuilt engine/ Are you positive that the governor gear to idler gear in the front of the engine was lined up correctly? If it is off just one tooth it can be impossible to time a magneto correctly. The magneto drive lugs should be at the 2 and 8 o'clock positions, there are pictures on here to show that but I don't have one on hand. You can search. The two small timing dots are on the magneto side but you can't see them with the seal in place. Those are helical gears so they "twist" as the governor goes in, making it hard to get them lined up. If the governor is removed, most find it helpful to place a paint mark on the correct teeth on the front side to assist when installing the governor.

[JustJim]

Hello again Friends-

Yes, magneto with internal coil. Coil was salvaged from my parts tractor. It was an unknown quantity, but throws a bright blue spark, and will jump a 3/16" gap on an old plug with the gap widened as a test, although at that point, it is a yellow spark.

Plug wires are new, best quality copper. I'm static timing, and begin by looking in the plug hole, see the #1 piston coming up with both valves closed, then continue until the second (TDC) mark on my keyed pulley is aligned with the pointer. Install magneto (rotor and drive gear marks carefully aligned), push mag up against the block, then hand crank one complete rev to TDC mark, then pull magneto away from block until the impulse trips before locking it down. I have checked (many times now), and #1 and #4 will arc right as the TDC mark coincides with the pointer. Number 2 and #3 plugs spark at a different location in relation to the TDC mark, (I presume that's normal), but they do arc as the impulse trips.

Governor drive slot is at 2 and 8 o'clock. I did have the governor misaligned by one tooth, but that was long before I tried to start it, and it has been corrected. I'm running out of ideas, but thought this morning I might check compression, just in case the engine shop accidentally handed me the wrong pistons or rings. They were all part of a kit, so it seems unlikely.

I do appreciate all of the kind help! Jim...

And hello to you, my amigo Pap!

[Glen]

Hi,
They have said on here that the spark should jump a 1/4" gap, and be bright blue, or white. A yellow spark is weak, and needs improving, the engine may not run.

It sounds like the coil is not putting out enough spark.

Try the spark test this way.
Fully charge the battery, if it hasn't been charged lately.
Remove the center spark plug wire from the distributor cap, and hold it, having the end about 1/4" from a bare place on the engine, be sure the transmission is in neutral, turn the ignition switch to on, and run the starter. The spark should be like I wrote above.


The Cub and LoBoy service manual says when measuring the float height of the IH carburetor, the gasket between the halves should be off. Don't measure with the gasket in place.

Below is a page from the Cub and LoBoy service manual, you can see in the pic at the upper left, the IH carb, it shows to measure without the gasket.
The Zenith carb, at the lower right, uses the gasket in place when measuring the float height.

http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

[Greenthumbfarms]

The Cub and LoBoy service manual says when measuring the float height of the IH carburetor, the gasket between the halves should be off. Don't measure with the gasket in place.

Below is a page from the Cub and LoBoy service manual, you can see in the pic at the upper left, the IH carb, it shows to measure without the gasket.
The Zenith carb, at the lower right, uses the gasket in place when measuring the float height.

http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

I seem to have been mixed up on what carburetor is measured which way. Thanks Glen

[BullDAWG]

Try the spark test this way.
Fully charge the battery, if it hasn't been charged lately.
Remove the center spark plug wire from the distributor cap, and hold it, having the end about 1/4" from a bare place on the engine, be sure the transmission is in neutral, turn the ignition switch to on, and run the starter. The spark should be like I wrote above.
http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

That works on distributors that have external coil but NOT on magneto with internal coil. OP has magneto.

[Rick Spivey]

Try the spark test this way.
Fully charge the battery, if it hasn't been charged lately.
Remove the center spark plug wire from the distributor cap, and hold it, having the end about 1/4" from a bare place on the engine, be sure the transmission is in neutral, turn the ignition switch to on, and run the starter. The spark should be like I wrote above.
http://www.farmallcub.info/manuals/gss- ... 002-09.jpg

That works on distributors that have external coil but NOT on magneto with internal coil. OP has magneto.

I see no reason this wouldn't work with a magneto, it works to start the engine if you re-connect that wire to the distributor cap.

[BullDAWG]

That works on distributors that have external coil but NOT on magneto with internal coil. OP has magneto.

I see no reason this wouldn't work with a magneto, it works to start the engine if you re-connect that wire to the distributor cap.

You AND Glen are correct. I've only worked on a SA w/ a wico magneto which the coil is internal and has no external coil wire. It's sorta like the GM HEI distributor. After looking up the J4 magneto on cubs I see they have a coil cover that has a plug type wire going from it to the cap. So it is possible to do as Glen said. But not on some A-M + Supers, 100-650's gas. Till just now I didn't know about the F4, F6, H4 or J4 magnetos.

[wrz]

I want to clarify one thing on your description : you rotate the second time and trip the mag at TDC is the rotor now pointing at number 4 plug wire in the cap?
Wm

[JustJim]

I want to clarify one thing on your description : you rotate the second time and trip the mag at TDC is the rotor now pointing at number 4 plug wire in the cap?
Wm

Hello-

No, I presume (given the firing order) that the rotor would probably be pointing at the #3. I can't see that, as I don't pull the mag away from the engine block to where it will trip without the distributor cap being in place. I was advised here that it was unwise to trip the impulse without a spark path to the plugs.

I did order a new coil. Didn't want to spend the money, but I'm running out of ideas. I also pulled the manifold and verified no obstructions. This tractor had mud dauber wasp nests EVERYWHERE, and it occurred to me that the manifold might have been obstructed.