rear wheel not engaging

if the wheel wasnt engaging you wouldnt be able to clutch start your bike...

When the motor is off and you turn the back wheel by hand (as though ur trying to clutch start it by hand) is there resistance when trying to turn it, as in can you feel the compression?
If yes then its likely your clutch/wheel is engaged.

Put the tip end of a screw driver to the middle carby and your ear to the other end of the screwdriver then when you twist the throttle grip are you hearing the sliding motion within the carby?

Take the intake manifold off and check to see if the gasket has been properly cut out.

Someone else here had the same symptoms as yours and they found that their gasket had the hole not quite punched out, and the paper slug was blocking off the intake.

If the intake checks out, check the exhaust system for blockage.

Sounds like your clutch might be slipping, check for some slack in the cable.

Maybe bad wiring?

I know I didn't ground my white wire properly, thought I had to connect it to something; boy was I wrong.

I would pedal, let go of the clutch, hear the engine running, stop pedaling, engine dies. Throttle would make a revving noise but only a small one which did nothing. Engine would only keep running if I continually pedaled.

If this sounds exactly like yours, possibly something to do with the white wire possibly making contact with something when it shouldn't, should be isolated (I taped mine up).

If this isn't it, I guess it would be something mechanical inside and my only guess is that which ever part of the engine that spins the small sprocket which turns the wheel is damaged or not functioning as it should be; thus engine powers, but unable to turn the sprocket to turn the wheel.

But you saying you can't throttle makes me believe this is more the case, or the white wire problem, as my guess is, even without throttle, your bike should just idle, not die; just a guess.