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M18C 350a

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Dman142

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Is there a resident Tohatsu member here who can help me out with the first generation 18hp? Having a heck of a time getting spark on this little guy. The service manual is toilet paper since it’s written in terms that most will not understand, nor do I. It is not very comprehensive in the service manual to actually troubleshoot.

I’ve replaced everything besides the exciter coil. It had to be from a 18C model with a Kokuson ignition. I can give all sorts of meter readings but don’t have a baseline to compare to such as DVA reading of 74 volts coming from the exciter. I have no clue on what the value should be. Can pull other voltages and ohm readings but again, same problem. No baseline.
CDI-replaced,
Coil-replaced
Pulsar-replaced
Flywheel is good.
Kill switch disconnected.

Any of the new exciters will not fit on this mode. It will hit the flywheel. Must have been a one year only model. I think it’s a 1984 model. The folks at Tohatsu said my motor is too old to give a date of production. Well, isn’t that just peachy. I repair stuff everyday and I can’t believe this little motor has got me stumped. Maybe someone can chime in for me.

It’s been many years since I posted on a place like this and I appreciate everyone’s input. Trying to sort through FB pages is annoying, especially with so many wrong answers people give out to fix something.
 
What does Brown to Earth mean? The brown and black go to the kill switch which has been disconnected anyways. It almost seems like something isn’t grounded and killing all forms of spark. That chart is about all I get for diagnostics. A certified car mechanic and master electrician couldn’t figure out what it means.
 
Small deflection means a cap is charging. Grounding brown kills ignition. 74 DVA sounds OK for the exciter.
 
I sit here wondering if the CDI box I bought is bad. The previous owner said it lost spark instantly and couldn’t figure it out.

It sucks because I am pouring money down the drain on a motor that really isn’t worth much. Was excited to see how it performs compared to others in the same HP range.

Is there anything else to try? Otherwise I’ll wait until I find another CDI I suppose. Motor super clean-spotless.

Tried a new coil too, no change. There’s only three parts and after replacing all, it’s still dead.
 
I sit here wondering if the CDI box I bought is bad. The previous owner said it lost spark instantly and couldn’t figure it out. I can pull voltages off each component.
Red to black: 70-74 (exciter)!
Blue to black: 8 volts (pulser)
Yellow to Tan: 8 volts (charge coil)
Red to Blue: 70-74 volts (exciter to pulsar)

It sucks because I am pouring money down the drain on a motor that really isn’t worth much. Was excited to see how it performs compared to others in the same HP range.

Is there anything else to try? Otherwise I’ll wait until I find another CDI I suppose. Motor super clean-spotless.

Tried a new coil and pulsar, no change. There’s only three parts and after replacing all, it’s still dead.
 
Looks like she’ll be put in the naughty corner for awhile will all sorts of parts next to her. Maybe it’ll magically fix herself and find the courage to run again. This winter I may tackle her again and when that fails, it’ll be parted out. Sad to see a mint motor get torn down to nothing. Oh well, on to the next motor.
 
Just for fun, I took an exciter coil that was too big but none the less, a Tohatsu from a newer system. I ground the exciter down so the flywheel would clear it. Everything went as planned, and it produced 80v, but still no spark. Tried the aftermarket cdi, no spark. Running out of ideas. I’ve grounded everything more than once also.

I am still under the impression the Oem CDI I bought is bad. That’s about the only thing now since the exciter is essentially putting out the same voltage. Drives me crazy.
 
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