Farmall Cub

Previously, I was able to start my tractor, but it would die like there was no gas. Switched carbs and no change, so didn't think that this was a fuel problem, hence the "tune up" option-maybe it's a bad condenser, etc?

So, I attempted to do a tune up on my Cub with J4 magneto: new points, plugs, condenser, wires.
Now, no spark to the plugs; however, when I remove the disty cap and the rotor and plate , I crank and I get spark at the points. Have NOT replaced the cap or rotor (but like I said, it was at least starting before, so don't think it's these?)

By the way (showing my ignorance) what exactly does the magneto do? it certainly wasn't in play when the rotor and plate were off, and the points still sparked when I cranked. Does it boost the voltage? BTW, no spark coming from Magneto upon cranking either.

Any input appreciated!

Charlie Drake, Potomac, MD

A magneto does not amplify spark, it produces it. Did you have spark from the coil tower before the tune up? Do you get spark from the coil now? The rotor does have to be timed.

Just because the carb swap didn't solve the problem doesn't mean it's not gas related. It could be trash in the tank that's settling over the outlet when you open the shutoff.

I had the same experience you are having and jumped from one perceived problem to another to no avail. Finally I adopted the KISS (keep it simple) theory. Starting at the fuel tank, I installed an in tank filter, a new fuel strainer assembly, an new steel fuel line, cleaned the carb and the metering valve following all the advice on each of those subjects on this forum. That was after pulling the head and freeing up sticky valves and adjusting them and checking the points, putting the spark plug wires in the correct order, etc, etc., etc. Results of my starting at the beginning, going step by step, and not jumping around I now have a perfectly running Cub. Don't get caught up in one problem after another. Start at the beginning and go thru it all. The results will be worth it.

Charlie:

I gotta echo BobM .. he has it down. Start at the beginning and work forward.

BobM wrote:I had the same experience you are having and jumped from one perceived problem to another to no avail. Finally I adopted the KISS (keep it simple) theory.

• Starting at the fuel tank, I installed an in tank filter, a new fuel strainer assembly, an new steel fuel line, cleaned the carb and the metering valve following all the advice on each of those subjects on this forum.
• That was after pulling the head and freeing up sticky valves and adjusting them
• and checking the points,
• putting the spark plug wires in the correct order, etc, etc., etc.

Results of my starting at the beginning, going step by step, and not jumping around I now have a perfectly running Cub. Don't get caught up in one problem after another. Start at the beginning and go thru it all. The results will be worth it.

These articles in the CBoK might be useful to you.

CBoK wrote:

• How To TIme A Magneto - Method #1
• How To Time A Magneto - Method #2
• How To Understand Firing Order
• How To Test Points
• How To Set Points
• How To Upgrade A Cub Fuel System
• How To Adjust Valves - Method #1
• How To Adjust Valves - Method #2

Keep us posted as to what helps in your situation.