i have not done this thing so i have no results/values to begin with.. so my words are a bit guess...when the ignition switch is on the neutral indicator comes on even when the bike 's engine is off.. and the neutral light is 12volts and 3.4 watts.. so it means you can connect any led's to it.. normaly leds are 3.3volts@20mA that means you can run max 50 leds from this as far as power is concerned (practically it will be less say 35-40 due to the voltage difference between vfd of led and the supplied voltage matching ) .. so i would say u can attach any or all leds to it..
now there is also a meter illumination light which illuminates the meter board... it works only when the headlight is on from the headlight switch and bike's engine is started... and it is rated at 12volts 2.4 watts... so u can run leds from it ..obviously you will need a proper current limiting on led .. be it using resistor or pretty regulator circuit..
now its prefrence .. what u want ..
if u want lights to come on when u just turn the key in switch to on you can do it.. by attaching leds to the neutral indicator bulb .. and relacing the neutral indicator bulb with led .. because if u dont do it the bulb would be either dim or would take all current and leds connected in parrallel from it wont turn on.. and connecting leds in series would obviusly limit the current to 20ma and the bulb is normally runing at 300+ mA...
dont attach leds in series with the bulb ..
or if u want the leds to come on when u start the bike engine u can attach the leds to the headlight switch ... a normal behaviour... where the meter is illuminated only when engine is runing and headlight is on.. if u go this way u should remove the meter board illumination bulb and use leds for it..
let the OP come with suggestions based on his findings.. then circuit can be built fro any choice..
i think that either way is ok..
but i havnt taken readings..