Petty made good on 23-of-31 pass attempts for 343 yards and ran for a score before exiting with a big lead as the Bears (6-0, 3-0 Big 12) surpassed the 70-point mark for the fifth time this season.
Backup Seth Russell completed 5-of-7 passes for 39 yards and scrambled for touchdown.
Lache Seastrunk rushed for two scores and Antwan Goodley made two TD grabs for the Bears, who improved to 6-0 for the first time since 1980.
Grant Rohach went 8-for-13 through the air for 70 yards, a touchdown and an interception for the Cyclones (1-5, 0-3).
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