Hi!
They all do that, Sir

This is the result of wetsumping, the oil drains down from the tank into the engine, and when started, it is pushed out of the breather (exiting through the breather hole behind the primary chaincase). The only remedy (except an oil tap in the feed line with all associated perils) is to check the oil level in the tank before starting and if necessary, drain the engine and refill the tank. An alloy sump plate with drain plug is a good investment therefore.
Cheers, Markus