I have always done the following :

1. Put bike on padlock stand
2. Pour petrol down top cylinder reed intake, fill to just under bottom edge reed valve square.

Remember that a proper leak down test would be the best since this test only shows you the the crank center seal is sealing from left to right and that the flywheel side crank seal is still OK.

The other side may still leak and you wouldn't know it. If it did however then your right hand side exhaust will smoke heavily because its now pulling the gearbox oil into the engine when running.

Bike will also be very difficult to start and when running, the one exhaust will run hotter than the other. ( Feel exhaust gasses with hand. )

If your bike starts 1st or second kick then I wouldn't worry too much....