The 24-year old Rubi, who finished behind Saulog in Saipan, took a firmer grip in the second heat after placing second to Dondon Yuson in the opening to win the title.
Saulog was relegated to second place and Yuson dropped to third.
Rubi is now setting his sights in the coming Mayor Robert "Bobby" Alquisola Memorial Motocross event in Barili this Sunday.
The memorial cup will be held as part of the Barili town fiesta activities.