Should I flush the motor?

[Animal Magnatism]

Just drained my first lot of oil for my new motor. There was a little bit of crap in it. Cleaned the filter, tank etc. (dry sump). Should I worry about pumping some fresh oil through the motor (by hand) before re-filling the tank? How much of the old oil would normally remain in the block / sump. Tank holds just over 3 gallons. Will whats left in the block / sump be enough to affect the new stuff.
Thanks.
Paul.

[Animal Magnatism]

Flushed it. Was a good idea. About 4 litres (1gal) in the system.