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How does a 2 cycle cdi work?

S

Sajoe

New member
I have a NISSAN 2 cycle, 3 cylinder, 1998, 70hp NS70C outboard I'm trying to get running. It won't rev above 3700 rpm. I've tried a shot of carburetor cleaner while running and it has no effect so I started checking the electrical system. The pulser coils are putting out the minimum acceptable value voltage but 2 cylinders are getting below minimum spark voltage and the third is getting no clear voltage. So it appears the CDI is bad. Unfortunately, this part does not seem to be available new OR used. Here's the questions. Even though the CDI isn't available, could a 3 cylinder CDI with the correct leads transplanted from the existing CDI be substituted? How can you find a suitable substitute? Any advice on how to get this engine running again would be appreciated. It has less than 100 hours on it and parting it out because of the CDI seems like such a waste.
 
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Did you check the exciter coil as well? Does your setup have separate ignition coils, or are they integrated into the CD unit? Depending on serial number, FOR 70C S/N 13002 AND HIGHER, the CD is still available new:
3N4061601MC.D. IGNITION UNIT 70C, ROUND PLUG$304.35

What method did you use to test the CD?
 
Are you using a DVA to test the outputs from the stator and trigger? You need a factory service manual to do a proper diagnostic before replacing any parts. If the cdi is bad you need to determine why it failed or you may cook the new one in short order.
 
My full story: After a couple of years of storage I try and start the engine without success. I pull the flywheel and find it threw a magnet and after trying for 6 months of attempting to replace the magnets or flywheel I re-glue the remains of the magnets and it runs and revs to about 3700 rpm and bogs. I do an air gap spark test and all 3 cyclinders fail at 7/16 gap but appear to function at 3/8 but #1 cylinder. I check the resistance of the spark plug coils exciter and pulser coils and all are per spec. Using a DVA I check output voltage of the coils and they are per spec but at the minimum. (exciter coil 139v/ pulser coils 3.03-3.3v) The ouput voltages to the spark plug coils are 110/117v for cyclinders 2 & 3 and #1 is readable. This leads me to beleive the CDI is bad.
 
TOHATSU changed suppliers for the flywheel, exciter, pulse coils and CDI at unit 13000. My engine is unit 10xxx. I have not found a direct replacement for mine (3F3060602M) and do not understand what would be different. Or different from a Mercury, Yamaha or Suzuki 2 cycle, 3 cylinder magneto CDI system other than terminals. Any enlightenment would be appreciated. As far as IF the CDI is bad please read below.
 
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