No spark and no electrical knowledge

Sat May 14, 2011 11:57 am

I had a running 47 Cub until a rod bearing disintegrated. I took the engine apart and replaced bearings, rings, etc. I also decided to take a look at the distributor and points, etc....now i have no spark. No surprise there. I really don't know what I am doing here. I'm not even sure what is what. I have attached two pics of my electrical system. I do have a 12V battery on a 6V starter. That is all I know. I need baby steps please. I have nothing to offer in return except I'll be happy to answer any medical questions people are afraid to ask their own doctor. I am happy to share my knowledge as a primary care physician assistant. thanks, david
You do not have the required permissions to view the files attached to this post.

Re: No spark and no electrical knowledge

Sat May 14, 2011 3:21 pm

If you recall, exactly what did you do to the magneto? The area around the cap looks like there is some sort of material used to create a seal. The cap must be positioned exactly in one spot on the magneto. Make sure you have the cap positioned correctly.
Last edited by challenger on Sat May 14, 2011 3:37 pm, edited 1 time in total.

Re: No spark and no electrical knowledge

Sat May 14, 2011 3:33 pm

I'm not trying to be funny but which part is the magneto?

Re: No spark and no electrical knowledge

Sat May 14, 2011 3:40 pm

The mag is the part that has the bump on top with the black cap on the back and with spark plugs wires coming out the back that are connected to the spark plugs.

Re: No spark and no electrical knowledge

Sat May 14, 2011 3:41 pm

http://www.cleancomputes.com/Cub/Cub%20 ... 5-1-49.htm

Operators Manual. Page 30 for the magneto.

Re: No spark and no electrical knowledge

Sat May 14, 2011 3:41 pm

This.
Image
Image from TM Tractor.

Re: No spark and no electrical knowledge

Sat May 14, 2011 4:00 pm

Okay, thanks. I'm pretty sure that I turned it at least once. If I understand correctly there are only two ways for it to go...one way and then 180 degrees. I have tried it both ways.

Re: No spark and no electrical knowledge

Sat May 14, 2011 4:10 pm

Actually, there is only one way it goes on. The cap has an indentation slot in the outer rim area that mates with a small protrusion on the mag.

Re: No spark and no electrical knowledge

Sat May 14, 2011 8:00 pm

David:

Check out some of these articles.. they will be of help for the electrically challenged -- and trust me -- I speak from experience :roll: :wink: :lol:

I am a bit anal I guess -- Mag = 6 volt battery. They are inexpensive. Also, I am not a fan at all of external coils.. they usually are a royal PITB. Probably while you are in there, it might make sense to check your internal coil and if truly bad - replace it. Don't throw away the core though as you will need that to mount the new coil to. They are readily available fromone of our forum members - Jon aka MagMan and a couple sites on the net such as MainelyMagnetos and Brillman.

CBoK wrote:
    Electrical

  1. How To Time A Magneto - Method #1
  2. How To Time A Magneto - Method #2
  3. How To Understand Firing Order
  4. How To Polarize Your Generator
  5. How To Polarize Your Generator With The Hood On
  6. How To Test Points
  7. How To Set Points

Re: No spark and no electrical knowledge

Sat May 14, 2011 8:52 pm

Basicaly you have a standard battery operated ignition system. Some place along the line the coil in the magneto has been disconnected and an external coil added.

A simple check first. Remove the wire from the side of the magneto. Remove the wire from the center of the distributor/magneto cap and lay it next to the engine block so that you have a 1/4" gap between the end of the wire and the engine block. Turn on the ignition. Touch the wire removed from the side of the magneto to the magneto. Then remove. If there is a spark the problem is in the magneto points.

No spark. You need a test light or multimeter to check out the ignition system. With ignition switch on, starting at the wire from the side of the magneto - start checking for battery voltage at each junction/connection - tracing the wiring back to the battery. Once you find battery voltage - the problem will be the previous appliance or wire between the voltage and the previous junction/connection.

Re: No spark and no electrical knowledge

Sun May 15, 2011 5:27 am

thank you all. i'll start working through the steps and reading through the articles. i'll make a new post if i am unable to find the problem.
take care,
david

Re: No spark and no electrical knowledge

Sun May 15, 2011 12:46 pm

I went through Eugene's test and did get a spark. So now off to the points. thanks again,
david

Re: No spark and no electrical knowledge

Sun May 15, 2011 3:05 pm

KenlyNC Cub wrote:I went through Eugene's test and did get a spark. So now off to the points.

Before you get to far ahead of yourself.

1. Trace the wire from the #1 spark plug back to the distributor cap on the magneto. Mark that tower. Then mark the metal part of the magneto directly behind the center of that plug tower. Roll the engine over to TDC #1 cylinder. Check to make sure the pointer and TDC timing marks line up. Then remove the distributor cap. The rotor's metal tip should line up with the mark you placed on the metal just behind the distributor cap. If not, rotate the engine one more full turn until the pointer and TDC mark line up.

2. Now you can remove the rotor to get to the points. I would clean up the points with a points file, check and reset the point gap.

Reassemble making sure the rotor is installed in the exact position prior to removal.

Caution. Sometimes it's easier to work on the magneto or distributor when removed from the engine. Caution again - do not rotate the engine. If you do remove the magneto - there is a video on this site demonstrating how to time the magneto to the engine.