A bad diode inside will cause the problem. The diodes job is to allow current to flow in one direction, its a one way street for electricity. If a diode goes bad the current flows both ways. That starter relay needs to go too.
The arrow show the direction in which the flow travels, the line crossing in front of the arrow is the blocker and nothing should back-flow. By unplugging the regulator/rectifier you'll know where to lay the blame for the drain.
If you view the pic of the regulator you'll see 3 yellow wires, a pair of green and a pair of red and a lone black. The yellow goes to the stator, green is ground and red to battery.
If you have a drain it will be in amps not voltage. The battery fully charged, but not while being charged should be close to a static 13.7 volts.
Connect a multi-meter in the amp function between the battery and the bike, (start on a high amp setting). all power to the bike must run through the meter. Do not try to start while using a amp-meter. this should tell you if there is a constant drain.
Clocks and such may pull a few milliamps, but if your batter is dead in an hour or so, you may have a bad battery or a short.
Charge battery while disconnected from bike, disconnect from charger, wait at least 48 hours, hook up to bike, bike should be able to start just fine. If it does not, the battery may have an internal short. Get a new battery.