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2nd Coil

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PACub100

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Dec 8, 2019
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297
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Woodbury, Pennsylvania
Got a question about the coil and what possibly may be ruining them.
Over the winter, I had my 1450 shut off on me at the end of my driveway while running the snowblower. It shut down like I'd turned off the key. After looking things over, I replaced the coil and it fired right up. Granted, I pulled one off my 100 and who knows how old it is, but today I was mowing and the Cub started acting like it was out of gas. I managed to get it up to my garage and now it's not firing at all.
I've ordered 2 Bosch blue coils but I want to make sure things are running right before I ruin one of the new ones. What should I be testing and what am I looking for?
My brother works with electric company so he'll be the one testing everything. I'll have him walk me through it and learn me how to do it... but for now I just need to show him what we should be getting.
 

Jay Fetters

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Jan 26, 2021
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U.P. Michigan
I've had the same issue with my 1650, I went through SIX coils this winter blowing snow in Michigan's upper peninsula. I still don't know the exact problem, I've checked everything I can think of, and replaced almost everything, including the key switch. I finally ordered all new ignition system and harness from Charlie (digger). I can't find the cause on mine, but if the ignition system is completely replaced, all it can be is junk coils. I tried from numerous brands, all with the internal resistor. I hope you have better luck than me with your diagnosis, and I really hope you post what you figure out!!!
 

PACub100

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Woodbury, Pennsylvania
I better not blow through 6 coils - wow! 😳

It could be something else, though my first thinking is the coil. It was running fine and then just like I was running out of gas...throttled down and it seemed to run ok. Give it more throttle, started to miss and sputter. After I shut it off, I tried restarting it, was looking in the carb and there's gas, so that meant weak to intermittent spark. Checked the plug - it looks totally fine.
Like I said, who knows how old the coil I took from my 100 is...it could have been going bad as well but managed to get me through till now. Just seemed kwinky-dink to happen again so fast. :unsure:
I'm going to have my brother stop in when he's around my house and have him check the resistance on the coil.

Once the new coils arrive, I'll also install Kirk's Transdensor that has been sitting in a box in my garage for the past year. I just got around to adding the steering upgrade (minus the thrust washer - I'll save that for a rainy day). :p
 

Jay Fetters

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Jan 26, 2021
Messages
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Location
U.P. Michigan
The first coil was on the tractor when I bought it. It went for almost two years, then all of a sudden I was just burning coils up. I'd test them and there was no resistance testing positive and neg posts of coils. Install new coil and I'd be good. The coils would last anywhere from a half hour to a couple hours. The one that is currently on the machine has been on for almost two hours now, and it's still going. Maybe I finally got a good one! I just received the harness and points, coil, condensor and what not this past Friday from Charlie. Now hopefully in the next month or two I can make time to get it installed and have a happy little cub.
 

Jay Fetters

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Jan 26, 2021
Messages
11
Location
U.P. Michigan
Mine would act the same way, a couple times it died just like you shut the key off, other times it would spit and sputter almost long enough to make me think it was fuel. I did the same as you, checked the carb, and since I was there I removed it and cleaned it and found nothing plugging the jets or restricting supply. So I tested for spark, weak at best, tested points and verified proper gap, ohm checked the points lead and it was proper. I checked the condensor, verified it was good, and checked the coil, and it was dead. SIX times!!! I've done this song and dance. I'm not sure if my key switch is not right while running, but it tests good on the bench. So I decided to replace everything now. Eliminating 45 year old wiring and connectors isn't gonna hurt a thing, and it eliminates one more variable in this conundrum.
 

dkirk

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Fond du Lac, WI
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David Kirk
The Quietline series of Cub Cadets featured a rubber-mounted engine. The ignition coil was mounted to the engine, thus all engine vibration is transmitted directly to the ignition coil. I'm convinced that coil failures on these tractors are all caused by vibration. The stock Delco coil was oil-filled and is thus prone to vibration induced failures. Two solutions are as follows:

1) Relocate coil to mount on the tractor frame or firewall.
2) Use an epoxy-filled coil such as the Bosch Blue. Epoxy potting supports the delicate secondary windings whereas an oil-filled coil does not.
 

mfrade

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Mike Frade
David brings up a good point, vibration is known to be a killer of ignition coils. I'd also wonder if the charging system wasn't maxing out volts / amps and adding to the stress.
 

dfrisk

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Dennis Frisk
I think DAVE may be on to something there. I had a 129 that the flywheel was missing 5 FIVE blower vanes in a row off the flywheel, it vibrated pretty bad, it was throwing things like the battery tray under the hood into metal fatigue. And a coil lasted less than 6 months. I bought replacements at cheap farm & home supply stores, and they didn't last as long. The Cubbies would shut down when the coils got hot after 30 to 45 minutes of mowing. I had TWO Cubbies cooling in the back yard waiting for one to start and run so I could more. I finally found a Cubbie dealer with Kohler coils and got them both running. This was several years before Dave started selling Bosch coils.
My personal record for number of coil failures in an afternoon is 3 THREE. One was IMPRESSIVE, the cooling oil inside the coil went shooting out the center tower of the coil like a geyser! And the oil was smoking hot. That coil wiped out the points & condensor too.
 

Greg Riutzel

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Jul 9, 2020
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Lebanon, Oregon
What should I be testing and what am I looking for?
1st off the coil primary winding resistance NEEDS to be at least in the 3.2-3.5 ohm range. It's better if it's 3.5-3.7 ohms. My present coil has no markings, I don't know if it's OEM, but the primary resistance is 3.7 ohms and never gets above a warm in temperature. Lower resistances shortens point life and makes for hotter running coils as single cylinder engines have a very long dwell time.

2 If you can, measure the primary ignition current. It should be around 1.5-2 amps but no more than 3 amps at worst. That to me is the BEST indicator of a functioning and properly matched coil ignition setup. Not only will coils last longer, but the points will like it too.

3 Condenser, or capacitor. Without a capacitance check function, it's almost impossible to check their health other than if it's shorted. Kohler mentions in the repair manual about deposits on the points of over or under capacitance as in mismatched or failing. Many DMMs will have a capacitance function of at least a couple hundred micro farads. A good condenser should read about .22, maybe .25 mfd. Most early ignition check meters, 1960s vintage, just have a zone on the condenser scale as a go no-go. What most do is if in doubt throw it out but I have some seemingly well made ones that are still going after 40 years and still test good.

As far as I can tell, there are NO coils with internal resistors, just different primary resistance by wire length. I beg to be proved wrong but the autopsies I've done I haven't found any yet and I don't believe for the wattage involved you could fit one in anyway. Yes, the world if full of literature about an internal resistor from vendors to Wikipedia but the reputable suppliers be they Walker, Delphi, Beru to more school related text books never mention it other than resistance; and coils are not transformers either.

The bottom line is the right coil has the right resistance to go the distance.
 
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PACub100

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Joined
Dec 8, 2019
Messages
297
Location
Woodbury, Pennsylvania
1st off the coil primary winding resistance NEEDS to be at least in the 3.2-3.5 ohm range. It's better if it's 3.5-3.7 ohms. My present coil has no markings, I don't know if it's OEM, but the primary resistance is 3.7 ohms and never gets above a warm in temperature. Lower resistances shortens point life and makes for hotter running coils as single cylinder engines have a very long dwell time.

2 If you can, measure the primary ignition current. It should be around 1.5-2 amps but no more than 3 amps at worst. That to me is the BEST indicator of a functioning and properly matched coil ignition setup. Not only will coils last longer, but the points will like it too.

3 Condenser, or capacitor. Without a capacitance check function, it's almost impossible to check their health other than if it's shorted. Kohler mentions in the repair manual about deposits on the points of over or under capacitance as in mismatched or failing. Many DMMs will have a capacitance function of at least a couple hundred micro farads. A good condenser should read about .22, maybe .25 mfd. Most early ignition check meters, 1960s vintage, just have a zone on the condenser scale as a go no-go. What most do is if in doubt throw it out but I have some seemingly well made ones that are still going after 40 years and still test good.

As far as I can tell, there are NO coils with internal resistors, just different primary resistance by wire length. I beg to be proved wrong but the autopsies I've done I haven't found any yet and I don't believe for the wattage involved you could fit one in anyway. Yes, the world if full of literature about an internal resistor from vendors to Wikipedia but the reputable suppliers be they Walker, Delphi, Beru to more school related text books never mention it other than resistance; and coils are not transformers either.

The bottom line is the right coil has the right resistance to go the distance.
I'm glad my brother is into electrical work... cuz once I got to "micro farads" my left eye started blinking uncontrollably and I think I drooled some. 🤣
Now ask me how to heat treat 7", 4340 bar to achieve 150-170 UTS at mid radius and I can hook you up.

All joking aside, I'll have him check the ignition current. We'll be replacing the coil, points and the condenser with the Transdenser.
(If I remember correctly, I believe the coil was pretty warm when I was checking everything out)
 

Greg Riutzel

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Lebanon, Oregon
Well theory aside, if a meter has the function I just pick a range and test. If numbers are good, then good to go. That's all what the old guys did.
 

JPrattico

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Dec 8, 2020
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167
Location
New York
displayname
Cubcadet_107
I’ve got a few NOS Kohler coils.
not the cheap stuff we are relabeled from China.
PM me if interested.
I got one of those on my 107, came with the tractor when I bought it. Sat for 30 years and it still works today.
:greenthumb:
Definitely high quality!
 

tkhoffman

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Oct 2, 2013
Messages
223
displayname
Tony Hoffman
My 782 went thru a few coils. A Harley Davidson coil has treated me good for 6 years now. However, one of the intermittent issues I had, aside from coil, ended up being a condenser that sat lose in the bracket. That equals a bad connection to ground. The bad Ground, made the machine miss a kick much like water in the gas. I would eyeball the wires at the points and condenser area as well as a snug fit, condenser and bracket
 
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