49 cub starter/magneto

Thu Oct 18, 2012 2:35 pm

hello,
Very much trouble starting my cub! When measuring resistance from ignition post on magneto to ground on machine is it suppose to be a short or open (ignition switch wire disconnected). I tested iginition switch and it works (open/closed) it is only a one wire connection. Seems something must be a miss because if this switch is suppose to short magneto to ground to kill engine and it already is a short when measured from the mag post to tractor frame then do I have a bad mag or what can my problem be. Thanks for any help you can give me.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:21 pm

firetech wrote:When measuring resistance from ignition post on magneto to ground on machine is it suppose to be a short or open (ignition switch wire disconnected).
Short.

I tested iginition switch and it works (open/closed) it is only a one wire connection. Seems something must be a miss because if this switch is suppose to short magneto to ground to kill engine and it already is a short when measured from the mag post to tractor frame then do I have a bad mag or what can my problem be. Thanks for any help you can give me.
The magneto ignition switch is a kill switch, provides a path to ground to kill/ground out the magnet.

Below a previous post on the topic.
viewtopic.php?f=1&t=72705&p=584995&hilit=magneto+wiring#p584995

Edit. In the run position the ignition switch is open, not path to ground out the magneto.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:27 pm

To troubleshoot your switch simply remove the ground wire from the magneto and see if it produces a spark from the coil wire.

Remember if you try to start the engine and it does start, you will have to ground the terminal to kill the engine or stall the engine in a safe manor.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:32 pm

If the magneto is already grounded internally like stated in previous post how does the kill switch work? I thought the kill switch was grounding the framework to the magneto hence killing engine.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:35 pm

lazyuniondriver wrote:To troubleshoot your switch simply remove the ground wire from the magneto and see if it produces a spark from the coil wire.

Remember if you try to start the engine and it does start, you will have to ground the terminal to kill the engine or stall the engine in a safe manor.


Can u explain further? I tested switch by itself and it is working fine (open and closes). but how exaclty do I test for that spark? Do I just pull any coil wire off?

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:51 pm

I retested the resistance of the lead comming from the magneto to the ignition switch and it is grounded the frame of the cub. Is that not exactly what the kill switch does - ground the magneto post to the frame work to kill engine? Any ideas as to what I can do now?

Re: 49 cub starter/magneto

Thu Oct 18, 2012 4:52 pm

Pull the high tension lead from the center of the distributor cap. With the switch wire removed from the mag, hold the high tension lead near the block and crank it over. Look for a crisp blue spark at a consistent rate.

Wear gloves or use an insulated tool to hold the high tension lead.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 5:07 pm

thanks lazyuniondriver I will try that. Going to be little tricky as I blew the starter during this whole process - guess the hand crank will have to do.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 5:09 pm

firetech wrote: Is that not exactly what the kill switch does - ground the magneto post to the frame work to kill engine?


Yes that is exactly what it does. The wire that connects to the magneto runs directly to the push pull kill switch. If the switch only has one tab, it is internally grounded. Pushing the switch in completes the circuit grounding the magneto killing the spark.

If the switch has 2 tabs, the other tab should have a wire running to a bolt or screw grounding it to the tractor frame. This switch is not correct for magneto tractors and works in opposite fashion, pull to stop, in to run.

If you have a crisp spark from the mag each and time it clicks while you crank, we'll pick it up from there.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 5:10 pm

I actually prefer to hand crank during this step of the troubleshooting process.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 6:36 pm

Do NOT "click" that mag over without somewhere for the spark to go. That will burn up the internal coil, which is pricey.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 7:42 pm

How far away should I hold this wire to the block for this to work? Is there a foolproof way to accomplish this test so as not to do any more damage? Sorry for so many questions but I have never done this before. I never had trouble with my cub before and it has always been good to me so all this a bummer for me. thanks for all your help.!!!

Re: 49 cub starter/magneto

Thu Oct 18, 2012 7:59 pm

Hold it about quarter inch from the block or filter can. If the magneto is producing spark, it will jump that gap.

Re: 49 cub starter/magneto

Thu Oct 18, 2012 10:05 pm

update......

well I just tested the mag and I did get a nice blue arc to the oil canister with every crank. I did have the ignition wire disconnected from the mag housing during the test. So now whats my next step? I still for the life of me cannot get my cub started!!!! I did clean my carb prior to all this cuz felt that might be my problem everything seemed in order but I am getting what looks like gas spilling from carb when trying to start it. I am not even getting a hard start - where it seems like it wants to start but doesn't. Also my cub has been exposed to rain for couple days while at camp. What am I missing?

Re: 49 cub starter/magneto

Thu Oct 18, 2012 10:24 pm

Well for starters:

firetech wrote:Also my cub has been exposed to rain for couple days while at camp.


Condensation in the carb is a good way to provide a no start situation. Plugs don't fire too well on water.

firetech wrote:I am getting what looks like gas spilling from carb when trying to start it.


Flooding it. Let it dry out a bit.

Check for condensation - sometimes visible on the side of the carb. Usually it is apparent when you take the carb apart. A whitish deposit will be present in the bowl indicating that water has sat in it for a bit (provided it was long enough). Yeah, been through this with Ellie this year. She sat for 6 months before I could get to her.