Sjaak started motocross in 1977.
After he started in 1980 with his goal to be able to ride at the highest level in the Netherlands, this goal was already within reach in 1982, but a nasty injury overturned this plan.
He then achieved his goal in 1985 and then it became clear that the follow-up plan to also be able to drive internationally would be quite a task on many fronts from a financial, physical and driving technical and mental point of view.
After an intensive discussion with his former manager and the questions he asked and the answers he gave, were an eye-opener and made him decide to stop the sport immediately and to focus on his social career.

During his participation in 1996, after not having been active in motocross for 10 years, he got the idea to see what the possibilities were to return to competition level one more time.
After some contacts with the Maico factory in De Bilt, the idea arose to return to the Dutch competition on a modest scale. Unfortunately, Maico ran into financial problems and the whole project seemed to end in failure. He did not give up and contacted the German Maico importer Kostler from Leverkusen and they were willing to support him further.
Sjaak started the competition strongly winning 8 races and with an interim promotion another 5 wins and another 2 podium places with the 500cc. In 1997 he also became Dutch champion.
Until 2003 he raced intensively at the highest level, but stopped due to private circumstances.