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Mark Dorcas

Member
Joined
Sep 7, 2020
Messages
15
Location
Aylmer Ontario
I recently bought a cub 129. It will not crank off the key but will crank if you jump the starter. It has a brand new battery, I will be replacing the coil. Is the key switch normally a problem. Any advise is much appreciated. Attached is a pic of my little gem.
 

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What the diagram will show is that when the key is placed in the Start position, the current must pass from the “B” terminal on the key to the “S” terminal on the key, and then through the PTO safety switch (deck must be disengaged), and then through the Neutral Safety Switch (foot must be on the brake), before the starter solenoid’s coil can be energized, provided the solenoid housing is well grounded. If the tractor were new to me, and I intended to keep it, I would (1) remove the solenoid’s mounting bolts and make sure solenoid was well grounded before replacing the mounting bolts complete with star washers.

I would then proceed to (2) clean the terminals on the Neutral Safety Switch and Ohm it out to make sure it was working well electrically and mechanically.

(3) With the battery installed and connected —but the Neutral Safety Switch disconnected— I would check to see if I had battery voltage on one side of the Neutral Safety Switch. (4) If I had the same voltage at the Neutral Safety Switch as I had at the battery (or nearly so), and I was satisfied the Neutral Safety Switch worked and that the spring steel actuator was present on the brake pedal rod and adjusted correctly, I would re-connect the Neutral Safety Switch, and the motor should turn over with the key.

(5) If I didn’t have good voltage at the Neutral Safety Switch, I would go back to the key, remove and clean (possibly replace) all the terminations, remove and Ohm out the key to see that “B” connected to “I” in the “ON” position, and that “B” connected to both “I” and “S” in the Start position. (Best Ohmmed out from wire end of terminals connected to the key with the battery disconnected.)

(6) Once I was satisfied the key was working, and that the terminations were secure mechanically and electrically, I would re-install the key and check for voltage at the Neutral Safety Switch with the key in the Start position (battery connected); again, if I had good voltage at the Neutral Safety Switch, I would expect the tractor to turn over with the key.

(7) If I still didn’t have good voltage at the Neutral Safety Switch, then I would go to the PTO Safety Switch; again, looking for solid terminations and good voltages and any wiring “anomalies” I might encounter along the way.

Of course, if your Neutral Safety Switch actuator is missing (as mine was when I first acquired my 149) you could easily bypass it temporarily, for diagnostic purposes.

Over the years I have encountered and resolved all the problems I describe above on one or the other of my tractors.

Hope this helps.:goof:

PS: If you can’t find either the Neutral Safety Switch or its actuator present on the bottom of your tractor, you may find two wires hanging down in the general vicinity, one of which might have a smidgen of electrical tape on it. Chances are, if you twist the two wires together, your circuit will be complete, at least that was the situation I found on one of my tractors.:goof:
 
I have zero experience with 129 bit on other rideons there is also a seat switch. It might crank but not start.unless you are doing something like sitting on the seat. Even in upside down Oz.
 
simple way to check for spark ...piece of wire with good sized alligator clips on each end...remove spark plug...one clip on threads of plug be sure it's not touching metal,one clip on GOOD ground..crank engine,plug should spark....if not then you have to check all components of ignition,start with another plug.(they do fail).If you have good spark then a quick shot of carb. cleaner should fire the engine briefly when cranked. If it fires on carb cleaner then your problem is fuel related.(note carb cleaner not starting fluid)
 
No spark condition could also be caused by corroded points contacts, especially if it's been setting for quite some time. It's fairly easy to clean the points contacts. Remove the points cover, (probably the hardest part of the process, well, that and replacing the points cover), run a piece of thin cardboard, like a business card or matchbook cover, between the points contacts several times and then check for spark. If they are really bad you may have to use some emery cloth like 600 or 800 grit, just use that sparingly one or two swipes on each contact.
 
You can take a 12v test light and hook it to the point side of the coil and it should flash when cranking the engine over. If the light stays on, points are not opening, stays off points are not closing. This will only tell you if points are closing or not, but not tell you if they are adjusted properly.
 
You can take a 12v test light and hook it to the point side of the coil and it should flash when cranking the engine over. If the light stays on, points are not opening, stays off points are not closing. This will only tell you if points are closing or not, but not tell you if they are adjusted properly.
The points are opening and closing. But may need cleaning or replacing. You guys are the best. Really appreciate the help.
 
So here is where I'm at. I have replaced and set the points @ .020 New coil new capacitor ( those aren't cheap) new spark plug gapped @ .025. Tractor cranks fine still no spark. I have cleaned every contact I can find what am I missing.
 
Did you clean the new points? Even new ones can be oxidized enough to not make contact.
 
OK, is there juice to the points from the coil?
Check with your VOM
If there is and they are working and adjusted correctly your test lamp should flash when cranking with it connected to the condenser side of the coil.
If the test lamp flashes you should have spark at the plug
 
It depends on the engine your working on but...your kill wire to the coil goes back to the switch for ground.disconnect it and look for spark.If you have spark you have a short in the wire (usually mouse damage) or a faulty switch. This means you may have to remove shroud to find the right wire but your already searching for answers, ( if it's a briggs).........you could pull the ignition switch plug and just run a hot wire to the coil for a test by jumping the starter direct (Assuming it's a kohler) You said coil good , points good, condenser good,plug good, only thing left is kill...
 
I apologize for all that input on the wrong engine....so simply it's grounded somewhere in wiring,in points,or condenser is NOT grounded.....if all components check good......I would still run a hot wire to coil to eliminate ignition switch problem....I'm not familiar will All points but many have insulating washers..I'll shut up now.....
 
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