Briggs Stratton Quantum 675 Ready Start

Hi.
Model 126T02 0368 B1
DOM MAY 2011

Ready start model, no manual priming no manual choke.

Engine always takes 2 pulls to start when cold.
1st pull nothing.
2nd pull engine starts immediately.

Engine operates perfectly.

When I turn off engine to empty bag and go to restart engine it starts immediately on first pull.

Question: Why does it take 2 pulls to start cold but one pull start hot.
I have checked basics.
New plug correctly gapped.
New fuel.
Auto choke fully closed when cold.
Choke thermostat working fine.

All advise welcome.

Thanks,
Nick.

Briggs Stratton Quantum 675 Ready Start