Im not from Michigan, but bought a bike in 2002 from a guy who rode under the same tent as Mark Hinkle for Montesa...1977-79.....the story of the Hinkle family was one of the most unbelievable Ive ever heard...perhaps you Michiganders remember him.....Mark was 1980 AMA Racing athlete of the year....he was joined by RC,Tim Ferry and James Stewart, among others...must of been really good, before he fell off the map.....
Know this is an older post but I will chime in with what I know about the Hinkle family...They were slightly before my time but were at many of the races I attended coming up thru the classes. Very friendly but misunderstood people. Almost motocross gypsies if you will.
Not uncommon for them to race 3-4 times a weekend chasing the Michigan District 14 titles in whatever classes they were in. Milan on Friday night, Saturday day race at wherever the event was, Saturday night race at Delta Ohio, and then back for The Sunday day race. Travelled in an older beat up motorhome with a Wells Cargo trailer.
Must have really burned through some gas in a weekend as they lived on the southwest side of the state.
Mark was the older of the two boys and rode mostly big bore Maico's in my day. Scott mostly rode 100'c and 125's on Suzuki's. Not sure if Mark won the 1980 500cc Amatuer National at Millville but I do know that Scott won the 100cc class that year. Pretty sure Mark won the 500 class in 1981 at Red Bud though. I don't believe either brother ever moved up to the pro ranks and I have no idea what they may be doing at this time. They were both extremely fast.
They are related to the Akin family, most famous of which is Lisa Akin. One of the pioneers of women's MX and a very fast rider as well.