# Advice on how to do a ign coil on a Ariens GT18 Kohler 18Hp Magnum?



## hankchill (Apr 15, 2019)

I lost spark on my Ariens GT18 (year unknown). I pulled off the black/white connector to rule out of the tractors wiring and safety cutoffs, still got not spark. Which would tell me its either the coil, magnets, or air gap. This tractor did run last night some im guessing the coil is shot. 

Everyone tells me its a huge job to do the coil and I have to pull the motor. I cant find too much info on how to do it. I dont want to just start unbolting things without getting an idea on what to do. Anyone have any photos or youtube links or a forum post on yanking out the motor? Its my first time messing with a hydro and a twin engine.


----------



## pogobill (Jan 31, 2012)

I can't help you much, but there are a few chaps here that rebuild lawn and garden tractors all the time. I'm sure you'll get some great advise before too long.


----------



## hankchill (Apr 15, 2019)

pogobill said:


> I can't help you much, but there are a few chaps here that rebuild lawn and garden tractors all the time. I'm sure you'll get some great advise before too long.


Thanks hopefully I can get some good info or at least clues.

I cant even find the flywheel or ignition coil on these diagrams, I must be blind today.
https://www.partstree.com/models/93...n-tractor-18hp-kohler-hydro-sn-000101-004000/


----------



## pogobill (Jan 31, 2012)

Check this out. You may find the specific manuals that you need/
https://www.ariens.com/en-us/manuals


----------



## FredM (Nov 18, 2015)

Have a look at electrical ll, and down at the bottom right hand side, look for alternator,(alt.) beside the alternator is a drawing of the coil and 2 leads going to the spark plugs, true if you don't know what you are looking for, the schematic is fairly hazy.

Your engine will be aircooled so will have a flywheel under the blower housing, remove the blower housing and you will find the ignition assembly air gapped to the outside of the flywheel,(not attached to the flywheel, but bolted to the engine).


----------



## hankchill (Apr 15, 2019)

So I started yanking the motor last night as its impossible to remove the blower housing otherwise, ill be chipping away it after work little by little.

So far I removed the hood and mounting frame for it...








Removed the belts for the mower deck drive (I believe)








Started on moving the controls panel out of the way but ran out of time. I still gotta loosen up the choke/throttle cables from the carb so I can slide it out of the way














After that getting to the main driveshaft bolts which I believe powers the rear wheels, steering, and lifting the deck up and down.








Thennnn hopefully its a matter of getting at these bolts and I can get it to slide forward







Also I found out to access those bolts there is a small notch in the frame. Found this out from a FB group member








I will be working on this thing all this week hopefully have get it sparking again soon.


----------



## hankchill (Apr 15, 2019)

So I finally got the engine out tonight it wasn’t too bad. However the motor mount bolts are in a weird spot.

I could see why people don’t want to do this too often. I hope an engineer get fired over this design.

I found a ton of mouse nest in here behind the fly wheel cover. The coil itself was loaded with grime and Oil. I’m wondering if that was the cause of my intermittent spark issue?? Does anyone know a way to test a coil I’m gonna replace it anyway after all this work.


----------



## hankchill (Apr 15, 2019)

Hmmm could this be the issue


----------



## FredM (Nov 18, 2015)

did you check the air gap before you removed the coil from the mount ?, looking at the gap in the second photo, shows this to be wide and if this was the case with a gap that wide at the magnet, this would most likely be your no spark problem.

I reckon I would be fitting a new coil to the engine after reading of the effort to remove the engine.


----------



## hankchill (Apr 15, 2019)

FredM said:


> did you check the air gap before you removed the coil from the mount ?, looking at the gap in the second photo, shows this to be wide and if this was the case with a gap that wide at the magnet, this would most likely be your no spark problem.
> 
> I reckon I would be fitting a new coil to the engine after reading of the effort to remove the engine.


I did check it and it was very tight. There was no way I was fitting .010 feeler gauge in between the mags and coil. That photo is deceiving I think check this one


----------



## hankchill (Apr 15, 2019)

Also im not looking forward to snaking in those motor mount bolts towards the rear lol. Who designed that!


----------



## hankchill (Apr 15, 2019)

So prices are around $200 locally and I found sites like this that list it for $119
https://www.kohler-engine-parts.opeengines.com/index.php?main_page=product_info&products_id=5035

Anyone know of a way to tell if its Chinese or not?


----------



## Bob Driver (Nov 1, 2017)

5258402S is the genuine Kohler part # for that coil and it's the same coil for most of Kohler's M series engines. Here's an Amazon link that list that coil for $51.95 + free shipping
https://www.amazon.com/Ignition-525...coding=UTF8&psc=1&refRID=BMDVQQJCHWANTRSYGXSJ

Here's an Amazon link to that coil that is more than likely Chinese at $32.99 + free shipping
https://www.amazon.com/Ignition-Mod...ZMQ4CRX2969&psc=1&refRID=5WDQTG4CKZMQ4CRX2969

DB Electrical sells that coil for $17.44 + shipping, but they are currently listing it as Out of Stock dbelectrical.com

Installed many a Chinese coil on customer machines over the years and never had an issue. It's like an old mechanic told me when I was first starting out... "It's not rocket surgery, it either works, or it don't and right now the machine don't run at all"

Air gap on a Kohler M18 is .010

I use a short tapered drift to line the engine mount bolt holes up, sometimes you can use two longer bolts of the next smaller size as "alignment pins" to wiggle/leverage the engine into place without damaging the threads…. 3/8 x 1 1/2 ---- Use 5/16 x 3. Kohler has started using self-tapping engine mount bolts on their new 7000 series engines like you would see on a deck spindle


----------



## hankchill (Apr 15, 2019)

Bob thanks for the info all very good stuff!!!!


I did realize something that may help with the install and removal. The holes for the back half bolts on the mounts are slotted. I’m guessing to leave them loose and slide the motor back. At least you can stick a wrench in after on the nut vs fishing around with a magnet attempting to start the threads.


----------



## Rob b (Aug 30, 2019)

hankchill said:


> I did check it and it was very tight. There was no way I was fitting .010 feeler gauge in between the mags and coil. That photo is deceiving I think check this one
> View attachment 48627


----------



## Rob b (Aug 30, 2019)

I often just use a index card for the gap, it always seems close enough. Those mouse nests are one of the most common reasons for small engine failure ,overheating.. If that air can't move around it will seize your piston.


----------



## Bob Driver (Nov 1, 2017)

There is a pump shaft for the hydro-drive on the fly wheel side like a 721 Grasshopper. The engine mount plate is slotted like that so you can take out the rear engine mount bolts and loosen the slotted bolts to cock the engine slightly to one side and get to the pump shaft bolts without removing the dash. Look real close at that thin plastic anti-vibration wafer that goes between the flywheel and the pump shaft as a reference. Try using the wear marks/dirt to get the pump shaft back in the exact same orientation to the flywheel as it was when removed. I've learned to mark them with a paint pin (too late now). Over the years, that shaft will develop a slight bow from torque. If you don't get it back in exactly the same orientation to the flywheel, it may have a noticeable vibration.

Flywheel mounted pump shafts are notorious for taking out the flywheel seal on the crankshaft because of this harmonic vibration. You probably don't want hear, but from experience, there is no way I would put that machine back together without changing that flywheel side crank seal

Don't know if you're old enough to know the history behind the Kohler's M-series engines. They are designed and look just like the Onan B43 & B48 engines, which where pretty much bullet proof. Over hauled a B-43 this summer that had over 4,000 hours on it and still ran strong. Here's a couple of pictures of B-series Onan engines. Look familiar??


----------



## hankchill (Apr 15, 2019)

Engines been cleaned out of the mouse condos and new oem coil has been installed with a .010 gap. Currently going through a memory loss lol with the driveshaft and flex plate. 

There was two studs and two bolts holding the driveshaft to the flywheel with the adapters. I remember taking the bolts out but what the hell were they attached to lol?? It almost doesn’t make sense to have them there but maybe they’re extra protection or something. Am I nuts as to where they go and what purpose they serve? Also do the two studs go through the holes on the driveshaft adapter?

















I should’ve paid better attention taking it apart


----------



## hankchill (Apr 15, 2019)

Anybody be able to tell me if this is right?










And what the hell did the nut and bolt go to asides from pulling the flex plate in place Lol?


----------



## FredM (Nov 18, 2015)

that is how I would put it together, your schematic shows you that, the nut you have circled in yellow will be to hold the clamp bolt in place, you would find that the drive shaft has a 1/4 moon recess under the coupling and the body of the bolt fits into this to hold the driveshaft to coupling.


----------



## hankchill (Apr 15, 2019)

So Fred at the time I posted this I wasn’t aware that the flex plate almost acts like a fuse and actually connects the driveshaft to flywheel. 

It makes total sense now but putting it back together last night it made zero sense so I had to stop hahaha.


----------



## Karl Tremblay (Jun 12, 2020)

hankchill said:


> So Fred at the time I posted this I wasn’t aware that the flex plate almost acts like a fuse and actually connects the driveshaft to flywheel.
> 
> It makes total sense now but putting it back together last night it made zero sense so I had to stop hahaha.


----------



## Karl Tremblay (Jun 12, 2020)

I think I have the same problem as you with my gt18 931033 Koehler magnum engine !For some reasons , after changing my solenoid because it was bad now I have a spark issue. Basically it will make sparks whenever it feels to do so! So I’m afraid I’m gonna have to pull out the engine to see the coil!It did it go hankchill? Was the coil your problem of no spark?
Thanks!


----------

