Ive had to drain my carbs a few times , heres a how to .
heres the fuel pump its in the way
remove its mount screws, not the lines
Tuck the fuel pump up out of the way.
Spot the drain screw on the end of the screw driver
just above the red heater plug connection , sorry its a bit blurred, Ive replaced mine with new types ,originals are allen screws, you need a ball ended key. Undo the screw until fuel and water drain out, about 4 or 5 turns, dont remove totally!
A small pencil beam torch will help alot to find the drain screws
Heres a carb drain point with a drain pipe fitted.
The whole job takes about 20 mins, fitting the pipe drains is a faff , heat the pipe ends and swell them out on a phillips driver before waggling into position.
Catch the drained stuff in a jar , water will be an obvious gob.
Cheers
Pod