wiring from a cdi tach signal

[Shadow250]

i'm to the point where i need to wire the crank input signal,

now i've read that when you have a cdi you can run from the tacho wire to get a signal but cannot run a signal from the coil.

but i've got a zzr250 (95) and the tacho circuit runs a 1 wire from the cdi to both tacho and coil 1. i've used my volt meter on the wire that goes to the tacho (after the split from the coil wire) and it reads 12v constant then when i crank it over it drops to 6v then slowly gains back up to 12v.

i'll load an image of the tach circuit for reference and hope i can get some answers as the info from MS only says you can use a cdi but from the tach signal only not the coils. but not if they are both the same damn thing.

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edit also there is a black green wire going from the CDI to the junction box which links to the starter circuit in the junction box

in the picture its in the bottom right to top right.

zzr250 (ex250) Wiring Diagram1.jpg

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2nd edit also what i dont really understand is the bike is supposed to be in wasted spark mode, but has 2 wires running from the cdi to coil 1 and 2.
but only one of those wires runs to the tacho (coil 1) so would that show that if i was to connect the opto+ into that wire running from cdi to tacho + coil 1 clipping the tacho wire and putting optoin+ in its place would it be a win or a boom.

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3rd edit. i just found something of interest but still dont know what to make of it really.. http://forums.ninja250.org/posting.php? ... 3368&tro=1
the guys here figured out that it is a sort of wasted spark mode. but with a 180 crank sensor. right down the bottom of the page shows what they worked out.

both cyls fire at TDC if its on a compression stroke or exhaust stroke, being a 2 coil system, and the tacho only reading of one coil. would that be a low enough voltage to pick up for the optin+ and not blow the box?

[dontz125]

The Ninjette uses a TCI (Kettering) ignition, not CDI. It is common usage to refer to any black box on a bike as "the CDI", but that is wrong in a vast number of cases. The RED wire in the wiring diagram (pic #2) is 12v from the key and kill switch to the coils; the BLACK and GREEN wires going to the TCI are the grounding leads that allows current to flow.

[Shadow250]

so that means i can use the direct off the coil method to run the micro squirt?

[dontz125]

Yes. See this thread for a discussion on this very arrangement, and an improved trigger circuit.