Kohler CH25 with fixed timing ignition: what aftermarket coils will work with this setup?

[austinyazookees]

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).

 

[StarTech]

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

 

[ILENGINE]

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

 

[bertsmobile1]

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

 

[Hammermechanicman]

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.

 

[bertsmobile1]

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.

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 .

 

[ILENGINE]

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.

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.

 

[Hammermechanicman]

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.

 

[StarTech]

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.

 

[austinyazookees]

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.

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