Cooper says practice on his start technique paid dividends at the most recent round.
''I got a lot more riding in between rounds as well and got my bike handling much better,'' Cooper said.
''I still think there is more to come as I didn't feel 100 per cent on track, so I'm looking forward to improving each weekend.''
Kawasaki rider Eli Tomac (US) and Frenchman Marvin Musquin (KTM) shared the wins at Mt Morris, and Tomac continues to lead the championship with 197 points from Musquin on 169.
Round five will be raced at Muddy Creek Raceway in Blountville, Tennessee this weekend.