If the plugs are new and you squirt starter fluid into carb and it still will not fire then you have a spark problem. Pull the plugs and recheck that you have a nice bright whitish blue spark. If it is an orange spark then you have a weak spark and it might just not be strong enough to set off the explosion. the coil, or the amount of voltage going to it, would be suspect in that case. Make sure that when cranking the coil is getting a full 12+ volts. Anything less than 8 volts is insufficient. Once the motor fires it can maintain on 8 volts.
As for the key not working it is a matter of hooking the right wires to the right terminls. For this you will need to determin which connection goes to where. You should have Off, on/run, start, common 12v+, and it should have negative continuity to the chassis.
Please see drawing for wiring information.
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