I've been ciphering 
Was thinking would it be better to try and adapt the 76 headlight circuit into the 73 on/off switch? That way the starter button wouldnt have to take the load of the light power all the time.
Is it possible TwoTired....... Or is that the way you made the conversion list anyway?
Geez, you sure want a lot from your internet access fees.
Not only an answer but an education, too!
The 73 starter button doesn't have the capability of routing the headlight power as the 76 button does. Rather it has a separate lighting switch that also supplies power to the headlight dimmer switch and then the headlight. The change I suggest, changes one connection for the starter, and moves one jumper that should already be on the bike, if you have given us the correct component inventory for your bike.
The K3 wiring routes power to the headlight fuse from the General lighting Br/W wire collection buss. This buss is powered from the lighting switch.
The K6 gets lighting power to the Br/W buss from the Black Buss with a direct jumper. (It's in the schematic I don't know where it is physically on the bike.)
However, the K6 routes power to the headlight fuse from the starter switch when it is not pushed. This switch get it's power from the Black wire buss which is energized from the ignition switch.
The K3 Lighting switch has Bk and Br/W wires which will perform the role of the jumper found on the K6, giving you master control over all lighting (after the ignition is turned on) This is how the K1-K4 operates.
Since the K6 expects Headlight power to come from the Starter switch (of which you have the wrong type) the disconnected jumper used in the K6 used to bridge power from black to Br/W is used instead to power the headlight fuse supply wire Bk/R.
The starter solenoid has four connections. Two big power in power out for the starter motor and two smaller connections. 12 V must be placed across these two terminals to energize the solenoid creating contact between the two big posts.
The Y/R wire on the K6 provide power the energize the soleniod via the stater button. The K3 bar control has Y/R wire for the solenoid and when the button is pushed it connects this wire to the G/R. This is why you must connect it the the Black wire buss powered from the key switch.
The last terminal on the solenoid must be grounded in order for the Y/R wire to have the desired effect. This is provided by pulling in the clutch (clutch switch) or having the neutral light on (neutral switch). The is supposed to be a diode that block the neutral Lamp voltage from getting to the starter solenoid and clutch switch on the K6. The K6 does NOT have the Starter motor safety Unit found on the K1-K4.
So, if I did it right, your controls should work like it did on the K3. All run lights controlled from the light switch. And, the starter button should activate the starter as appropriate.
This enough of a ramble?
