yamaha xj550j electronis

the previous owner of my bike tried to rewire it and messed up, and
when i tried to start it i smelt burning things, i got a aftermarker
CDI box and an wondering, since it once had lights but now doesn't can
i just wire the CDI from the magneto and make it just send juice to the
coil

 

What magneto?

 

in the service manual it refers to it as the CDI magneto, it is like a
generator to charge the battery to run the lights

 

Maybe the XJ550J (it's a Maxim, right?) has a CDI, maybe it doesn't.
People call electronic ignition systems that run off of 12 volts "CDI"
when they are just an electronic ignition unit.

The AC generator is an excited field alternator. In order to put out
enough electricity to charge the battery and light the headlights, you
must have a battery installed in the motorbike.

When you turn on the ignition switch, battery voltage goes through a
power transistor in the voltage regulator. The voltage goes through
carbon brushes into the slip rings of the alternator rotor. That turns
the alternator rotor into a rotating electromagnet when the engine is
running. The elctromagnetic field induces AC voltage in the stator (the
part that's not turning). The AC voltage is rectified into DC voltage
by six power diodes in the voltage regulator (that's the finned
aluminum thing on the left side of the bike, if you have one). When the
battery voltage rises to about 15 volts DC because it's being charged
the power transistor shuts of and 12 volts doesn't go to the brushes
again until the voltage drops below, say 14.5 volts DC.

On the other side of the engine there are two signal generator, or
"pulser" coils that signal the electronic ignition box to cause the
spark plugs to fire. Those coils only put out about 2 volts, they
wouldn't qualify as a CDI magneto.

But, look at the wiring harness coming from the stator of your AC
generator. Does the connector have three wires going to it, or five
wires? If it has 3 wires, that's just the ordinary 3 phase wye wound
stator.

If it has 5 wires, there may actually be a separate CDI winding in the
stator. Some Hondas have that. I never saw a Yamaha with DCI yet.

If you don't have a battery in the system to excite the rotor's field,
you wouldn't get much voltage out of a separate CDI
winding. The AC generator's rotor would have to have strong permanent
magnets installed in the rotor. If you touched a screwdriver to the
rotor the magnets would grab it and hold it.

I don't think you actually have a CDI ignition system. CDI magnetos
send anywhere from 50 to 500 volts to the CDI ignition box. And the
coils don't get any voltage until the pulser coils tell the coils to
fire.

A regular electronic ignition system sends 12 volts to the coils
anytime the ignition key is on.