How can I get a wiring diagram for a Kawasaki KFX 450R?

your wiring schematic and service manual are here

https://www.manualslib.com/manual/850224/Kawasaki-Kfx450r.html?page=422&term=Wiring+Diagram+%28Ksf450B9F+Eur+Model%29&selected=1#manual

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Does the motor spin or just the starter spinning.
Please reply back on here... I will help you trouble shoot it and get it running!!
Steve

When you "hot wire" an ATV with a battery is the same as leaving the key on 24-7. This is not recommended..A good locksmith might be able to help you resolve your "switch issue"
BUT.. the brown wire and the gray wire(both are ignition switch wires).. connect them and you should have power

I had a similar problem on one of my bikes. Turned out a "Test Port" had rattled loose between the carb and the intake. I threaded a screw in the hole to prevent the leak and problem was resolved.

Kawasaki Ninja 250 R Owner Manual

cdi...ignition coil and all switches, run stop switch contacts may be worn, last resort..cut and tie together those two wires on switch, bet thats the prob

if it has a carb, clean it.

have a compreshion test done on the engine first if its good say upto150psi look for a fule problem and a new set of plugs wont hert it chech that the air fillter is clean