Hi Jules and Bill
it's because the bike has only done 19 miles that I would be worried about flushing oil too.
It's the first few miles that will create the small particles of metal from the running in process that the sludge trap will catch, also other than what was said somewhere what proof is there that the bike has only done 19 miles, has had the engine worked on at all or been stored unused for whatever time.
If it were mine I'd be for putting the cash for flushing oil towards a tear down but know how it is to want to get on the road, suggest you buy some cheap non or low detergent oil, change the oil, give it a short fire up or small run and change the oil again, if it sounds good then enjoy it.
oil that's stood still for 30 years will have gone through many many temp and humidity changes (even in the engine) so will be full of water, water = rust on steel bits (bearing cages, gears, cams and so on)
best of luck with it though - enjoy