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CH25S no tach after MDI conversion

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Hey there Simplicity experts, Just bought a 700 hour Legacy 25 for $600. Really in pretty good shape. Bad head gasket, fixed that (both while at it) and toasted ASAM module (would only run one side). So... Kohler's answer is the MDI upgrade with new coils and a different flywheel, $130, no problem. Now it runs like a champ, but no tach. Kohler tech rep told local repair shop that there was nothing that you could do because of the style coil used and the tach signal came from the ASAM on the original design. Anybody have any ideas for a work around? Not sure what kind of tach signal the dash unit on these takes.

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On a different note, did you have the heads machined before replacing the head gaskets?  I'm betting they're warped.  I had .009" removed from each of mine to make them flat again & I had NO head gasket blow.  Valve seats & seals replaced also.

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Shaun, I did not. Didn't want to put that much time into it not knowing what else might be wrong with the engine. (Turns out, probably nothing except the ignition). The new style head gaskets are a huge improvement over the originals. The metal fire ring on the new version provided much needed reinforcement where the gasket is thin near the oil return galley.

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Update- So I dug out some old pulling tractor parts, namely leftovers from a home made electronic ignition build. A Mopar pickup unit, GM HEI (early 4-pin) module and a HEI 4 cyl single pole coil. Screwed the Mopar pickup to a pc of plywood and inserted a bent over nail to act as a signal pole (driven by drill just to test) AND IT WORKS! (sort of) The system will drive the tach, but only with the coil hooked up. If I attempt to run the coil from the coil output terminal on the HEI module directly without the coil hooked up it doesn't carry enough signal voltage to run the tach. The solution I think is a "pull-up" circuit to supplement the HEI signal wire to the tach (a problem/solution commonly encountered/incorporated in modern LS1 engine & electronics swaps into older GM vehicles).

The plan??? If the pull-up runs the tach ok on the test unit I have room to mount the Mopar pick-up behind the electric PTO clutch. I'll just drill and tap the steel crankshaft spacer to accept pins to drive the pick-up. I should be able to run the tach signal circuit (HEI/Mopar pick-up) from any switched 12 volt source.

 I KNOW... a lot of work to go to just to have the tach work. But hey... its there it might as well work. Besides, I'm only out $5 for a 20 pack of resistors. The rest of the stuff came from the parts bin.

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Where there's a will, there's a way - and you proved it.

But I have to ask, why do you need to know engine RPM's while operating the tractor?  Usually you can tell if the engine's bogging down by sound.

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