Who is the

Yes , It's my MX idol Håkan Carla Carlquist 79, 250 and 83, 500 MX Worldchamp,

It was to easy I think.

In 1977 he suffered a bad bad kneinjuri and the docktor was told he never can motocrossing anymore, he take a big bite in the apple and fight his way back from the
injuri and won motocrossing back and the 250 worldtitle in 79 on a Husqvarna worksbike and become Yamaha 500 faktory rider in1980 on a decent rear suspended bike, he had to fight with the Yamaha ingeneers development to make a new rearend
design instead of the old triangulate suspension and won their intrest to make a new bike with adjustable link system for the 81 season, then he got the 500 title in 1983.
He ended his career in 1988 on a private Kawasaki ride.
In 1988 he made a classic on the race in Namur, he lead the race so much he could stop and drink.
Today he lives in France and is 55 years old and suffering from old injuris.

yes that is Heikki Mikkola, 500 champion in 1974 and 77,78, 250 champion 1976, on Husqvarna 74,76 and Yamaha 77,78 .
great photo anyway.