Cub starting problem - I'm stumped

[James]

I need help with my Cub! It wouldn't start, just turned over but no spark. It's a 1948 with 6 V positive ground. I checked the ignition switch and found that it was faulty, so being cheap I bought an ordinary push-pull switch to replace it. The new switch has two terminals rather then one terminal and a ground, so I ran a new wire from the second terminal of the switch back to the positive terminal of the battery. I tried it - nothing! Now it won't even turn over, even without the switch installed. What the heck could be going on?

[Bigdog]

Your old switch with one terminal was a kill switch or grounding switch for a magneto ignition system. The 2 terminal switch is for battery ignition systems. If you are trying to start the tractor with the switch pulled out it will never start because it is grounding the points. You can either leave the switch in the off (or in) position and start the tractor or replace it with the correct switch. Your 2 terminal switch operates backwards from the single terminal switch.

[James]

Thanks for the quick answer. I see that part of the problem is that I am stupid. Oh, well. Hmm.. If the switch is open to start there must be something else wrong as well, since the old switch was showing open in both positions when I tested it, the tractor should have started. It used to start quite well, then all of a sudden one day it just wouldn't spark. Has anyone experienced that before?

[Bigdog]

You might want to open up the disrtibutor on the mag and check the points. Magneto systems are usually pretty reliable and sudden problems that crop up are easy to track down and fix. The kill switch wire may be shorting out somewhere. Try disconnecting it at the post on the side of the distributor and see if it will start. Pull the center wire on the distributor, hold it close to ground and crank the tractor over and see if you have spark. Check back and we'll work through this.

[James]

Finally I've had some time to work on the Cub. One problem was the battery would no longer charge - got a new one. Still won't start with the kill switch wire removed from the magneto. There is plenty of spark on the wire to the distributor. I was looking at the drive gear on the rotor and noticed it seemed fairly worn. Maybe it's not turning properly. I tried turning the engine over with the distributor cap off and the rotor was turning but it seemed pretty slow. I was surprised that the rotor and its drive gear are plastic!

[Carm]

I would verify that you are getting a spark at the plugs. Make sure you have the copper core wires as the resistance type can severely limit your spark. I had a similar problem. New wires helped. I then replaced the coil and now its great. The distributor will turn more slowly than the engine, that is normal. Make sure also, that you can hear the mag impulse coupling snap for each firing position. Verify the firing order as well.

[James]

My spark plug wires look almost new, so I don't think that's the problem, but I will check to see if the plugs are sparking. There is also a bit of carbonization on the distributor cap contacts, I noticed. The central contact is especially dirty looking. What can I use to clean these?

[Rudi]

James:

I use the Canadian Tire Electronic cleaner - spray type. Some very fine sand paper - 220 or finer and just touch up the contacts.

Check the points for proper gap and the condensor. Condensor's don't usually go, but I had to replace Ellie's a little while ago.

Hey, welcome to the Forum!

[David]

Hi Big Dog

I read your reply on the position of the switch. I am a little confused now. I have a 48 cub with Mag ignition, and for this one, the switch is pulled-out to make her run.

Now, just last Saturday I picked up a beaten up old 61 cub with battery ignition. When I went to try and start it, I pulled the switch out (assuming it is the same as my other cub). But it didn't run. I also pulled the plugs and no spark. Thinking that the switch might be defective, I pulled the grounding wire off the distributor, but it still didn't start/spark.

Tomorrow I am going to replace points etc, but I guess I want to check about the switch position. Should it be pulled or pushed to run with the battery ignition? What about the grounding wire on the distributor? Should I remove it to take the switch out of the circuit (just like the mag ignition).

Thanks

[splicer]

David, my '57 is battery ignition and it needs to be pulled out to run. Don't know about the Mag. types.

[parts man]

David, the wire to a distributer is the power wire, it needs to be connected in order to get a spark. The switches both are supposed to be out in the run position, for a mag switch (one contact) that means its an open circuit, for a distributer switch (two contacts) it is a closed circuit.
Check to see that you are getting power to your coil with the switch pulled out.

[David]

Thanks. I will check. That's good advice. Seems like a really small wire for power, that's why I thought it is ground, just like the mag.

[Bigdog]

Hi Big Dog

I read your reply on the position of the switch. I am a little confused now. I have a 48 cub with Mag ignition, and for this one, the switch is pulled-out to make her run.

Now, just last Saturday I picked up a beaten up old 61 cub with battery ignition. When I went to try and start it, I pulled the switch out (assuming it is the same as my other cub). But it didn't run. I also pulled the plugs and no spark. Thinking that the switch might be defective, I pulled the grounding wire off the distributor, but it still didn't start/spark.

Tomorrow I am going to replace points etc, but I guess I want to check about the switch position. Should it be pulled or pushed to run with the battery ignition? What about the grounding wire on the distributor? Should I remove it to take the switch out of the circuit (just like the mag ignition).

Thanks

David, with the mag switch, in the out position, the switch contacts are open. With a standard 2 terminal switch, in the out position, the contacts are closed. The switch contacts must be open to run on a mag system.

[James]

Well, last weekend I checked the points, adjusted them a bit (they look to be in good shape), cleaned the distributor, put everything back together, and I was getting good spark at the plugs, but no startey!. I checked a plug after turning it over a few times, and noticed it was dry. My almost new Zenith carb must be plugged with crud. That was the first thing I thought of when it wouldn't start, so I took the carb off and blew it out with air, but it didn't help. I guess I'll have to take the carb apart and soak it in carburetor cleaner. Does anyone use a gas additive or use higher-octane gas to avoid this problem?

[LYNYRD]

I use a product call Chem tool on one of my cubs that had not been used for approx. one year.