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This is my first post here, I am doing an engine swap for a friend. He had a Kohler CH25S and bought a brand new Kohler CH730. It was supposed to be a basic engine swap and now it just wants to fight me.

I know the original motor ran but threw a rod (I drove it like that into the garage) and has the "smart" ignition system. The new motor has fixed timing. The engine harness connector and wire colors match, there is power to the coils. I pulled the plug and grounding it to the motor while cranking gives me an intermittent faint spark. I've tried extra grounds from the engine to the chassis and the battery to the chassis.

Is there any additional wiring that needs to be done to accommodate the different style ignition system?

Any help would be appreciated.

TD or Not TD said:

This is my first post here, I am doing an engine swap for a friend. He had a Kohler CH25S and bought a brand new Kohler CH730. It was supposed to be a basic engine swap and now it just wants to fight me.

I know the original motor ran but threw a rod (I drove it like that into the garage) and has the "smart" ignition system. The new motor has fixed timing. The engine harness connector and wire colors match, there is power to the coils. I pulled the plug and grounding it to the motor while cranking gives me an intermittent faint spark. I've tried extra grounds from the engine to the chassis and the battery to the chassis.

Is there any additional wiring that needs to be done to accommodate the different style ignition system?

Any help would be appreciated.

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Welcome... hopefully this "fight" can get sorted, you read as knowing
your stuff

You dont actually point to what the engine swap is creating as a problem.
Is it trying to fire at all, like fuel feeding that "faint spark... or no joy at all?
Wiring wise, if you are getting any spark at all, as you report you are, then
'safetys' for "smart ignition" should be closed (contacts)... maybe a wiring
diagram for the machine would help there?

Trust that prompts more info for all to chew on

KK

The engine will not fire what so ever. Before I found out there was no spark I got the plugs wet. I pulled the fuel line off and was using strick starting fluid so I can control the "fuel". The battery is charged, terminals are on the correct posts as I have read that if they were reversed it would crank but have no spark. I called a Kohler dealer and the only advice they had was to check the grounds or add a ground.

I'm not used to working on small engines. Mostly modern muscle cars.

Since the machine ran before the swap I assume the chassis wiring is good. The kill switch was been bypassed by the owner, the engine has oil pressure while cranking.

If I have to I will remove the flywheel, coils and harness from the original engine to this unit. I just don't want it to void his warranty.

If you applied battery voltage to the magneto, you need to buy a new one. That external power will kill it in a very short while. The only wire you need to connect is the 'kill' wire that grounds the ignition when the key is in "Off", and may also connect to the throttle control linkage on the carburetor. Some have a 'kill' built into the throttle control that grounds the ignition if the control is moved to the very slowest speed.
The advance system may have used 12v, I don't know, but the magneto does its own power generation.
You might be able to fit the SAM onto the new engine, but I would not want to try to figure that out from where I am seated.
tom

I have not applied power to anything. I have only tried additional grounds. I used a basic test light to check for power. How much signal is supposed to be at the coils?

I have never used a test light on a magneto system, so have no idea what you'd see. Given that it generates juice to power a field coil, and then removes that to create the spark, it is a pretty simple machine. It would need one end of the coils grounded, which might be accomplished with the mounting screws. One coil provides field energizing power to the other coil, which does the sparking part, FWIW.
If you leave all the wires that do not have a bare ring-type connector loose, it should spark when twirled. The ring type is a full-circle connector that goes under a bolt or screw to obtain a permanent ground.
On the CV I own, there is only one wire that leads off the coil, and it goes into a connector that leads off to the carb & ignition 'kill' terminals. There might have been a ground wire, but I don't remember one particularly. It is really very simple.
If you have more wires, then you likely are looking for AC and DC outputs for lights & battery. The manufacturer should note which connections are which, and the tractor manual wiring schematic should note the applications so you can match them up.
tom