2016 Kawasaki klx125 D-trecker

Description:

2016 66 plate Kawasaki klx125.
Bought for my son as a bike that nearly starts, knowing abit about bikes, and as it attempts to start, I thought no problem.
Haven’t been able to get it running.
It attempts to run and nearly does but bogs out badly and backfires until it cuts out.

Since owning we have replaced;
Fuel injector, no change.
Fuel pump in the tank, no change.
New ngk spark plug, no change.
Had the throttle body and sensors off, cleaned through every hole.
Checked wiring from ignition to ecu,
Replaced relays and fuses,

Given up abit and he just wants a working bike so il put it up for swaps for a similar looking bike, nothing smaller than a 70cc.