Mike Barnettís introduction into auto racing came as a Junior High School youngster, when he and Nebraska Auto Racing Hall of Fame inductee, Jim Riggins, were given a 1948 Ford Coupe, which they quickly fashioned into a race car. As both of them were too young to drive at the time, they had to hire a driver in order to race the car at the former Lincoln Speedway in Lincoln.
In 1970, Riggins purchased a home-built Modified frame and over the next few seasons, the pair raced the Chevrolet-powered machine at several different tracks in Nebraska, Iowa, Kansas and South Dakota. In 1971, the car placed second in the C feature at the Knoxville Nationals and that same year, Barnett was voted Mechanic of the Year for the Nebraska Modified Racing Association.
Barnett and Riggins raced together through the late 1970s, with a highlight of their racing relationship being a second place finish at an Outlaw event in Oskaloosa, Iowa a few days before the 1977 Knoxville Nationals. The pair finished fifth in track points at Knoxville that same season.
Barnett also prepared race cars and engines for successful drivers Ed Bowes, Mike Brooks, Rex Hendrickson and Don Droud, Sr. Droud won the track championship at Midwest Speedway in 1984 in a Barnett-prepared Sprinter and also won Eagle Nationals and the Labor Day Sprint Festival at Midwest Speedway the following season in a Barnett car.
In the late 1990s and early 2000s, Barnett became the Director of Competition for the Nebraska Sprint Car Association.