In short: an American motorbike racer, very talented, former world champion 250 cc (1990) and Superbikes (1997). Used to have a reputation as a bad boy.

A bit more detailed: this man is considered very talented, even by those who do not like him very much. The author does not know much about his American national career (please provide me some information, if you can), but from the time John entered the world championship, he was controversial. His words and deeds were provocative. This is where he earned his reputation as a bad boy. Much to the disappointment of his opponents, he won the 250 cc world championship in his first full season, on a Yamaha.

His transition to the 500 cc was not so successful as his 250 cc adventures. Eventually, he went back to the 250 cc, only to return to the 500 cc after several races to race a Cagiva, giving the Cagiva team their first dry-race victory.

After Cagiva had to quit the 500 cc championship due to financial reasons, John couldn't find a satisfactory ride for the following season. So he went waterskiing in 1995. In 1996 he returned, to the Superbikes this time. He started the season with a double victory for Ducati, and finished third at the end of the season.

The next year, 1997, saw John race to the world championship in the Superbikes class on a Honda RC45. The first, and so far the only, man to win both a two stroke and a four stroke motorcycle racing world championship, since there are separate two stroke and four stroke world championships. As a reward (part of the contract?) John got a ride on a Honda NSR in the 500 cc world championship in the following season, 1998. That season did not go as John intended.

In the 1999 season, John teamed up with Erv Kanemoto in a small budget team: using Max Biaggi's 1998 Honda NSRs, and without a major sponsor. Two smaller sponsors saved the season financially, at the last minute, but the results have not been satisfying: one pole position and a second place in a race.

After more than half a year of waterskiing (again), a blonde John joined the Vance & Hines team in the American Superbikes series, with a bit of success: two pole positions and a second place in a race.
The AMA series are tough and John hadn't had any preparation at all, when entering the series in the second race, in the 2000 season.

For a long time it looked as though John was going to ride again in AMA in 2001, on a Ducati for the Competition Accessories team. He was fastest in December 2000, during the Daytona Dunlop tire test, where all the important riders were present.
However, John and the team could not reach an agreement on the contract. It looked like John was going to do other things.
But, surprise, surprise, John has signed a contract with Yamaha Racing, to test ride the new Yamaha four stroke bike, to be raced in 2002.

Despite what people might think, John is not the bad boy he used to be, if ever he was one. Off the track he is quite different than on the track, as can be said for many other professional sportsmen. According to himself, he is now much more relaxed than he used to be. Over his career, he has alienated quite some team mates and owners, due to his 'undamped' so to say words and deeds.

His honest and straight from the heart approach also give him a certain charm, at least for those who do not have to work with him. It is refreshing to see a character like John in the racing world, and it would be a much duller place without him.