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Hi all. New to forum. But reading some of the threads here, I think I've finally come to the right place for some answers about fixed ignition coils.

I have an old (as in 2000ish vintage) Yazoo Kees ZTR with a Kohler CH25 V twin engine with a fixed timing ignition system, i.e., no SAM.

I bought it a while back from a mower repair guy outside Waco (I'm in Austin, about 100 miles away, saw it on side of road while driving back from Dallas, bought it on a lark). Repair guy had modified it with a push button starter after the ignition switch starter mode failed (though "on" position still works to power the harness), so wiring harness has been modified (the oil sentry oil pressure sensor on the breather has also apparently been disabled/bypassed as well but not the oil level sensor).

The tanks totally clogged up, but have since rebuilt the entire fuel delivery system. New tires all around as well. Replaced the main seal and rebuilt the breather (as I was thinking the main seal oil leak was caused by pressure blow from a broken breather reed). So I am vested in the ZTR now.

It's served me well for almost a year.

Cranked it up after sitting the winter to cut an acre property I have. It ran a bit warming up (with help from some starter fluid to get it going), then it suddenly stopped running, so checked the three things an ICE needs: compression, fuel, spark.

Compression and fuel are good, but spark appears inconsistent: weak to non-existent, both using a tester (automotive -- the HFT in-line spark type with a very faint orange light) and directly thru the grounded plug (sometimes a spark, sometimes not).

I want to replace the coils first and see if that is the issue, but apparently Kohler doesn't offer the simple single blade coils for the fixed ignition system on the CH25 anymore: instead, Kohler makes an ASAM/MD (something speed something module / magneto discharge?) retrofit kit (24-755-308-S) that includes new 2 blade coils, some new harness wiring and a new flywheel/magneto -- and is priced accordingly, i.e., expensive.

I am not too motivated to go retrokit and replace the flywheel (yet), so I would like to see if I can find some aftermarket coils that are compatible (even if they requires modification like rewiring or an additional resistor in-line) with the CH25 fixed ignition setup.

I've read about some aftermarket coils that work with some modification -- two specifically, one suggests adding a 4K ohm resistor in-line to get the coil resistance up-to-spec, and another suggests just disconnecting the kill ground wire to the coil altogether and just letting the carb fuel cutoff shut down the engine.

I'm looking for anyone who has the same system and has found some coils that will work -- even with some modification.

Thanks in advance for any help you might be able to provide me.

Lets start with the model and spec number from the engine. Can be hard to read on Kohler sometimes so may have to get creative. Then we can decide what your options are.

There a couple different ignition systems Kohler used on the CH engines. Do you have the engine numbers? If it is a DASI system you can get a kit to replace the coils with MDI ones that are just standard coils. Regular Kohler coils won't work. 32 707 01 s is the kit number if you are replacing a DASI system. If it is an ASAM system then the kit with a flywheel.

Thanks for the reply.

There are no tags/numbers I can find ANYWHERE on the engine: remember, it may be as much as 20 years old, so if it was on a tag, then it is likely long gone (though the stamped metal Yazoo Kees model and serial number tag is still riveted to the chassis near the engine -- see attached photo).

From the service manuals -- and the fact the coils have a single blade connector and there is no SAM. The diagram calls it a
Capacitive Discharge (Fixed Timing) Ignition System. Is that the same as a DASI?

BTW, I found these aftermarket single blade coils that claim they are compatible with the CH25. Do you think these will work?


Interestingly, on the coil I pulled out of the cowl (brand INEL? part no. 32 584 01), the coil pickup/sensor is corroded and completely flush with the coil body, while on all the versions I have looked at online, the pickup extends a bit (1-3mm?) from the plastic body of the coil.

Current PN for that coil is 24 584 45-S

If you want take on it not working here is an after market on eBay (RipBay)
https://www.ebay.com/p/1464553075?i...MIo7XGvYmv6AIVE2yGCh3wHAxZEAYYASABEgIr5PD_BwE

OK, now that's good news. Thank you so much for that old part, new part cross-reference.

I actually read the reviews on this eBay listing before posting this thread, and they were actually quite useful/insightful. It's where I got the idea/insight about the internal resistance issue with these vis-a-vis the discontinued 32 584 01 coil and ways to work around it (by either just disconnecting the kill wire/blade or by putting a 4K ohm resistor in series to get the resistance up to where it needs to be -- did you see any other solutions suggested in the reviews?).

I never heard of doing that as the Kohler coils have internal steering diodes and don't need such an added part. Even the Briggs coils only need a pair external steering diodes to prevent them from interfering with each other. Must be a poor design if it needs to be done.

austinyazookees said:

Thanks for the reply.

There are no tags/numbers I can find ANYWHERE on the engine: remember, it may be as much as 20 years old, so if it was on a tag, then it is likely long gone (though the stamped metal Yazoo Kees model and serial number tag is still riveted to the chassis near the engine -- see attached photo).

From the service manuals -- and the fact the coils have a single blade connector and there is no SAM. The diagram calls it a
Capacitive Discharge (Fixed Timing) Ignition System. Is that the same as a DASI?

BTW, I found these aftermarket single blade coils that claim they are compatible with the CH25. Do you think these will work?

Amazon.com: Carbhub CH18 Ignition Coil for Kohler CH18 CH22 CH25 CH620 CH621 CH680 CH740 CV18 CV20 CV620 CV680 CV730 SV715 SV725 Replace Kohler 24 584 01-S, 24 584 04-S, 24 584 45-S John Deere MIU11542, M132370 : Everything Else

Amazon.com: Carbhub CH18 Ignition Coil for Kohler CH18 CH22 CH25 CH620 CH621 CH680 CH740 CV18 CV20 CV620 CV680 CV730 SV715 SV725 Replace Kohler 24 584 01-S, 24 584 04-S, 24 584 45-S John Deere MIU11542, M132370 : Everything Else

www.amazon.com

Interestingly, on the coil I pulled out of the cowl (brand INEL? part no. 32 584 01), the coil pickup/sensor is corroded and completely flush with the coil body, while on all the versions I have looked at online, the pickup extends a bit (1-3mm?) from the plastic body of the coil.



View attachment 51159

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That is not corrosion it is a different design
When the high silicon transformer steel core rusts it starts between the laminations causing them to fan out .
This is just an older design where the need to save money was not so great.
Rust on coils is not a problem unless it gets so thick that the core contacts the magnet as it passes .
The steel used will rust sitting on your workbench while you watch it .
It is a trade off as to how far the legs extend past the actual coil.
Too close and you get insufficient cooling
Too far away and you reduce the intensity of the magnetic flux that the coil windings are exposed to.
That particular set up looks like it is a rebuildable one . Many of the early ones the laminations & the coil were 2 distinct pieces so you just swapped the coil section when they went bad
In fact they were a 3 part system as trigger chip was a standalone part .

StarTech said:

I never heard of doing that as the Kohler coils have internal steering diodes and don't need such an added part. Even the Briggs coils only need a pair external steering diodes to prevent them from interfering with each other. Must be a poor design if it needs to be done.

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As the reviews say it works fine as a single it is most likely from a different engine and just happens to work with Kohlers .
Briggs are trying to force all the old Power Torq engines to be scrapped. They did it by upping the price of the magneto coils to $ 180 wholesale a price no one will pay for a push mower coil
Thus the search for an alternative supply by downloading catalogues form the factories, there are a lot more of them than I though so it is back to pirating old mowers

I am guessing that Kohler is doing the same as Brigs, i.e., forcing obsolescence, by discontinuing the 32 584 01 coil for a fixed timing system and in its place offering their (expensive and intensive-to-install) retro kit if you want to stay correct.

I am going to try the other coil recommended in this thread and will report back.

BTW, I ohm'ed the coil I pulled off (in the pic) and it measures infinite/open between the kill switch blade and ground (the metal attaching body of the coil) and between the spark plug boot connector and ground. Though the Kohler CH25 service manuals (I have two different ones; it appears one is for the DIYer (80ish pages, 3.5mb) and the other for a repair shop (200ish pages, 6.5mb)) do not provide a specific resistance tests/specs for the single blade/fixed timing coil (only tests and specs the 2 blade smart spark coils), I think that the measurements I did do indicate that the coil has failed?

Slight correction on the continuity test results.

I got out the multimeter and tested the coil again (under the old measure twice, cut once adage)

When measuring from the kill switch blade to coil metal mounty body (ground), it appears that my multimeter is "diode sensitive"

When I go:

+ on blade and COM on ground I get open/infinite
COM on blade and + on ground I get 1055 ohms (right between the 2 blade spec range of 945 and 1175)

So there must be a diode in the coil circuit -- and my multimeter must recognize that.

Either way, the spark plug connector-to-ground still shows as open except when the multimeter is set all the way to 20M ohm range, and then I get a reading of 15-16.5M ohms (2 blade spec is 3750-7000 ohms).

Actually you are getting a reading on the primary only because of the diode. That secondary reading is definitely bad.

Not so much forced obsolescence as parts manufacturers stopping production of a certain part or goes out of business forcing Kohler to moving on to company B, but Company B doesn't make the part that is compatible with Company A, but by that time Kohler has moved on to Company C for parts production, Which is somewhat forced the 3-4 ignition type changes on Kohler engines with their different ignition types

The problem with taking measurements on modern magneto coils is while the secondary is always connected so that is fine you have the chip on the primary .
That is equivalent to reading an old coil from the other side of the points and not knowing if the points are open or closed or just touching .
So it is a moot point because if the primary is faulty it makes no difference if the secondary is good or not

I never really understood why Kohler needed to try and make variable timing ignition systems. All of which seem to have problems. I have replaced a few DASI systems with fixed coil retrofits. Can't really see a difference in how the engines ran. I guess that's why i am not a design engineer.

Hammermechanicman said:

I never really understood why Kohler needed to try and make variable timing ignition systems. All of which seem to have problems. I have replaced a few DASI systems with fixed coil retrofits. Can't really see a difference in how the engines ran. I guess that's why i am not a design engineer.

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In theory and in practice you get a better power curve under load with a variable ignition.
I ride a lot of old motorcycles that have either fixed or manual ignitions and you can really notice the extra torq when you retard the "right" amount gong up hills .
The units that Kawasaki fitted the the D series JD engines are a cut above the latter engines in long grass .

Hammermechanicman said:

I never really understood why Kohler needed to try and make variable timing ignition systems. All of which seem to have problems. I have replaced a few DASI systems with fixed coil retrofits. Can't really see a difference in how the engines ran. I guess that's why i am not a design engineer.

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The truth is they have all been playing with variable timing for several years but just kept quiet about it. Kohler started it with the ASAM which was the equivalent of a distributor with vacuum advance. But almost all the engine manufacturers both 2 and 4 cycle have been using it for years. And there is a higher failure rate with all of them compared to the old fixed timing systems. And some of those failures are not complete failures. they will make an engine run rough because the electronics starts playing with the timing at the wrong times. Or will kick the rev limiter in at very low rpm's causing a misfire but not complete loss of spark.

I understand the power curve thing. I just think kohler missed the mark with over complicated, expensive, unreliable ignition systems on an engine designed to run at WOT all the time that is 3200-3600 RPM. Not complaining, the new kohler stuff is like ethanol gas. It makes me money. On the mowers i replaced the DASI with standard coils the customers didn't notice a difference.

Just like variable duration lifters gives you better performance with mild racing cams. I was quite happy with the 265 V8 after install the variable duration lifter, mild racing cam, 350 lock-up transmission, and install the turbo exhaust.
I went from 16 mpg highway to 32 mpg cruising at 55 mph. I ended up with an average fuel 22-23 mpg combined city/highway. With the improved fuel economy also with quite a bit torque improvement so I actually had more takeoff response.

One thing to remember too is that; although, most of the engines at peak design rpms there are cases where the engine are under different loads at different times along with different rpms.

It is like the introduction of fuel injection some of the very first small engines like the Robins were complete failure reliability wise but the fuel injection systems are making a lot improvements especially that many don't even have an O2 sensor. Robin actually went back to a carburetor design. I have worked some EFI v-twins from Kawasaki and Polaris that works quite well; although, the Bobcat that was in limp mode gave me a fit until I found the parking brake was out of adjustment.

Hammermechanicman said:

There a couple different ignition systems Kohler used on the CH engines. Do you have the engine numbers? If it is a DASI system you can get a kit to replace the coils with MDI ones that are just standard coils. Regular Kohler coils won't work. 32 707 01 s is the kit number if you are replacing a DASI system. If it is an ASAM system then the kit with a flywheel.

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The coils I bought that were single spade and claimed compatibility with a CH25 did not work.

Is it possible the magneto magnet is bad? It seems strong and pulls the coils down onto it pretty tightly when positioned under them.

Going back a couple of posts, Hammermechanicman, is ASAM (analog spark advance module?) the same as a fixed timing CDI.

Per the service manual, my configuration -- no 12V to the coils, only one spade on the coil and that's for the kill switch wire -- seems to be called a fixed timing CDI -- or more specifically, from Figure 8-4. Capacitive Discharge (Fixed Timing) Ignition System. So it appears that an ASAM is not the same as a CDI (fixed timing system).

You mention you do a "standard coil" downgrade/conversion from a DSAI: would those standard coils work for me as well (as you are basically ripping out the DSAI and throwing it away, right)?

I searched the service manual for keyword ASAM: the hits on the search show a control module and a two spade coil, which I do not have.



. So if those coils are NLA, I need the ASAM kit with

Thanks for all the posts.

After a further detective work, I have new information on my issue. I'll put it here and repeat on a new thread as well.

I reached the small engine shop (literally "The Small Engine Shop") that sold me the Yazoo Kees (thank you Google streetview, got the phone number that way).

The engine is a CH25-68533.

It was upgraded/converted from an ASAM (or at the shop owner thinks at least it was an ASAM) to an MDI.

As it is a 25HP Command Pro, the ASAM->MDI kit per Kohler PB-265 would have been 24 755 308-S, which includes a flywheel and ignition modules/coils and some wiring.

I don't (think) I need a new flywheel, just the coils, but I can't seem to find the part number for these MDI coils.

Does anyone know what ignition modules came with the ASAM->MDI?

Thanks in advance for any help.

I think but not sure the MDI coils in the ASAM conversion kit are the same coils in the DASI conversion kit. A couple weeks ago i converted a CH15 from DASI to MDI. I could not find a kit for a si hle cylinder so got the kit for a twin so i have an MDI coil and a CDI coil i can put side by side and take a pic if you want. A standard CDI coil will not fit the DASI flywheel. The gap will be too wide and wrong arc. Not sure which flywheel is in the ASAM conversion kit. Can you post a pic of the modules you have you need replaced?