GPZ 750 wiring

What makes you think you have weak spark?
Did you use an adjustable spark gap tester?

 

Also, I'd say that a voltage drop from 12.0 to 7.5 is indicative of a weak battery.

Anything much lower than 9.5v cranking suggests a weak battery or resistance (possibly bad ground on the motor?

I'll check for grounds but it's a brand new fully charged battery so unless something is strangely wrong with it then it shouldn't be that

Just for posterity I went and completely sanded off the ground at the ignition coil, the right back side of the motor, and the one at the starter solenoid but I'm still dropping to 8.5v on crank

A new battery can be bad. If you connect your meter to the battery posts, not the cables, and then turn on the key and press the starter button, the initial reading before turning anything on should be at least 12.5 and should not drop below 10 or 10.5 with the starter engaged.

Where are you getting the 8.5v reading 

At the wires going into the ignition coils
I pulled the battery out of my daily riding motorcycle and got the same result, low voltage at the coils

Grab your voltmeter
DC V
Key ON
Kill Switch set to "RUN"
Engine running

red probe on positive battery post
Black probe on red wire at one coil
what is your voltage?
voltage should be as close to 0.0V as possible
any higher than 0.5V is too much resistance

move black probe to the other coil's red wire
what is the voltage?

move red probe to negative battery post
black probe to a bare metal part of the engine

what is your voltage?
should be close to 0.0V as well

F64 wrote:

Grab your voltmeter
DC V
Key ON
Kill Switch set to "RUN"
Engine running

red probe on positive battery post
Black probe on red wire at one coil
what is your voltage?
voltage should be as close to 0.0V as possible
any higher than 0.5V is too much resistance

move black probe to the other coil's red wire
what is the voltage?

move red probe to negative battery post
black probe to a bare metal part of the engine

what is your voltage?
should be close to 0.0V as well

Key on I have .252 between the positive post and both red wires, 0 between the negative post and engine ground, I assume you meant this state not with the engine actively running, if I need to hit the starter it'll have to wait till morning tomorrow as it's a bit too late in the house for the ruckus 

The ground measurement needs to have the bike on but it doesn't have to be running, but current needs to flowing to something(like a headlight).
So you should redo the ground reading tomorrow morning with key on, kill switch "run", engine running.
no need to wake the neighborhood tonight.

The coil measurements needed a running bike because I wasn't sure if the igniter or junction box would cut power to the coils if the bike wasn't running.

Your red coil wires are ok resistance wise. not great, but your bike should run ok.

I am, like the others above, curious about your battery's condition.

tomorrow morning
meter on DC V
key on
kill switch"on"
engine not running

red probe on the positive battery post
black probe on negative battery post
what is your voltage?

hit the starter button
what voltage does the battery drop to while the starter button is pushed?

what is the voltage at the battery when the bike is idling?
what is the voltage at 3000 rpm?

turn bike off

The bike isn't generating enough spark to have any audible ignition let alone get it idling or have it run up to 3000rpm

I'll give the ones I can a shot come sun up