Doesn't sound like your wiring. The dash connector, brake light feed and number plate lamp are all isolated when the ignition is off anyway, so unlikely to cause a drain while bike is standing. (That is unless you have pulled out the key in the "P" position!)

Check the battery first. Remove it, fully charge it, disconnect charger and measure the voltage across the terminals. Then measure the voltage across the terminals at hourly intervals (with battery still removed from the bike) and record how fast the voltage drops off. It should fall back down steadily over 24 hours and stabilise at 12.5V(ish) for a good battery. If it continues to fall back and goes below 12V, or it falls very quickly then the battery has bad cell(s) and is goosed.

Once you have checked the battery is OK and you have a picture of what its own internal voltage drop/rest voltage is, connect it back up to the bike and measure the voltage across the terminals (do not turn the ignition on/off though before measuring voltages*). Check the voltage over time and compare with that of the disconnected battery battery. Comparing the two sets of voltages will allow you to calculate the static drain on the battery.

*Bare in mind that for the first 24 hours after the ignition has been switched off the imobiliser will draw a small current (while led flashes), after 24 hours it becomes idle (LED stops flashing) and current draw becomes nominal. Just be wary that the measured voltage drain will vary depending on how long since the ignition was switched off.

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