[1] In 1953, he ended his career as a motorcycle racer due to a serious leg injury sustained on the Sześciodniówka.
[3] During this period, Jankowski developed the first Polish racing car built from scratch, designated Rak 650.
[6] In 1963 he co-initiated the Cup of Peace and Friendship, which was held until 1990, in which drivers from socialist countries competed[7][8] After the international regulations changed from Formula Junior to Formula 3 after 1963, Jankowski began developing a car to that specification.
[9] The result was the Rak 64, with which Jankowski won the Polish championship title in 1964 and the inaugural Cup of Peace and Friendship.
[12] In total, Jankowski was the author of 23 racing motorcycle and car designs and 19 patents.