Honda 300 won't start off the key

solenoid on starter motor .

if your battery isnt dead (try boosting it) then check to make sure the car is in park all the way and try again if nothing happens you need a new starter. alot of people dont put the shifter all the way back to park and that keeps it from starting.

check your battery connections then charge the battery over night then check the charging system

I think you may have a immobilisor problem try the spare key first

Take the starter off for testing. If the lights were normally bright, and went dim when key was in cranking position, it means the start circuit is working-battery power is going to the starter, but it won't do anything. The starter motor is probably bad.
Good luck.

About the only thing you didn't mention was the starter itself. You could have it tested. But before that, try to see if you have power on the small wire to starter solenoid on the starter, when key is held in cranking position. Pull the small wire off and check for power with a multimeter or a testlight while someone holds the key in crank. This is the signal wire from ignition switch that closes the elec. contacts inside solenoid so the starter gets full power from the battery to spin. (This wire also is in the circuit with the clutch switch and the starter relay.) If you have power on this wire in crank, it is very likely the starter is bad. If there is no power, check that circuit out. It is losing power somewhere from switch to starter solenoid. Good luck.

Starter motor solenoid replaced or replace bushes.

Probably an intermittent ignition switch. Try start it by connecting a wire directly to the starter solenoid and touching it on the + of the battery. Ignition switch must be ON and be sure the car is NOT in gear.
LPG

The click you are hearing is the starter solenoid. This solenoid is a relay that applies 12 volts (at high current) to the starter motor. When you turn the ignition key you apply 12 volts ( at low current) to the solenoid. If jiggling the key solves the problem all of the time I would suspect the ignition key assembly.
If jiggling the key only works some of the time I would suspect the solenoid/starter assembly. For your info the solenoid/starter comes as a complete assembly, when you buy it.

Hope this helps

Loringh