Nippon Denso Tachometer

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Highside

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I scored a Nippon Denso Tach that was off of a John Deere snowmobile.

Can this be adapted for use on the XS?

I'm assuming that the snowmobile was a 2 stroke twin, so does that mean that it will only read 1/2 of RPMs unless I have a waste spark ignition system??

BTW, the part # is: 100569-1160 & JD # AM55015.

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if your bike has 2 coils, maybe hook up both coil wires. put a diode on each wire??? id hook it up first and see what happens
 
yamaman said:
if your bike has 2 coils, maybe hook up both coil wires. put a diode on each wire??? id hook it up first and see what happens
Click to expand...

That's what I was thinking too. I'll leave the factory tach in there, then hook up this one and see if it's reading half of RPM's. If not, then intall it as-is. If so, then hook up both wires with diodes.
 
Hi!
Most 180 degree 2-stroke twins for snowmobiles have wasted spark CDI magneto ignition systems, consisting of 1 trigger coil, 1 "Black Box" and 1 dual output coil. In some cases the coil and "Black Box" can be in one unit.

The flywheel then has 2 magnets or "lumps" activating the trigger coil, giving 2 sparks per crankshaft revolution.

An XS with points has 1/2 spark on each coil per crankshaft revolution, with the TCI (late model electronic ignition, with flywheel trigger) it has one spark per crankshaft revolution)

Either way, you will get incorrect reading. Also, as CDI primary voltage is way higher than battery/points/coil ignition, it may not read at all....

But it may still be possible to make it work, but that requires more electronics knowledge than what I posess. I once purchased a "Krober" racing tach for my -75 RD 350 with points ignition (1 spark per crankshaft revolution). Later I fitted a "Boyer" ignition to the bike, with "wasted Spark" (2 sparks per revolution). Then I sent the tach to Krober for recalibration. This indicates it can be done, it just requires detail knowledge...

Good luck with this mod, please post your findings, positive or negative!

If this tach does not work out, a UK made "Scitsu" racing tach most likely will, but is at least $250.....
 
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