1973 FIM Motocross World Championship

Roger De Coster won his third consecutive 500cc world championship for Suzuki ahead of West German rider, Willy Bauer. The championship wasn't decided until the final race in the Netherlands, when Bauer suffered a mechanical breakdown, losing the championship to De Coster by two points.[1] Kawasaki joined the world championships with Brad Lackey in the 500cc class and Torleif Hansen in the 250cc class.

Suzuki's defense of the 500cc world championship was dealt a setback when, the FIM announced a new motorcycle minimum weight limit of 209 pounds just before the start of the season.[2] European motorcycle manufacturers competing in the championship complained to the FIM that Suzuki was spending millions of dollars to build lightweight motorcycles that the smaller European manufacturers found impossible to compete with.[2] Suzuki had already developed and built their race bikes so, there was no time to build new bikes. As a result, Suzuki resorted to adding ballast to the bikes.[2] Unfortunately, these alterations threw the bikes out of balance and caused them to lose traction.[2][3] To make matters worse, Maico and Yamaha had developed new rear suspensions with longer travel which helped transfer power to the rear wheel over rough terrain.[2][3] The Suzuki management felt they were being unjustly treated by the FIM and were slow to react to developments by the other manufacturers.[2][3][4]

Most of the Western European riders boycotted the Austrian 500cc round due to heavy snow on the track.[5] As the season got underway, Yamaha's new "monoshock" rear suspension began to make an impact with Christer Hammargren winning a moto and Jaak van Velthoven taking the overall win at the Finnish Grand Prix.[2] De Coster won both motos of the Italian Grand Prix but, Bauer came back with a hard fought victory in Czechoslovakia, relegating De Coster to second place in both motos and took the lead in the championship points tally.[2] Bauer then took control of the championship by winning 5 out of the next 6 motos.[5] Suzuki management's frustration at their perceived unfair treatment led to a lapse in support and, Suzuki team riders De Coster and Sylvain Geboers then took matters into their own hands by modifying their motorcycle's frames and developed new rear suspensions.[2][3]

Going into the final race of the season at Sint Anthonis, Holland, Bauer was still holding the points lead but, the Suzukis were showing improvement. The Sint Anthonis track was composed of deep sand which robbed engines of power and increased fuel consumption.[2] A Suzuki engineer calculated that their bike's gas tanks did not have sufficient capacity to finish the race.[2] De Coster then took one of their tanks and drove two and a half hours to have the tank modified to increase its volume.[2] He then drove back in time for the race. Despite having little sleep, De Coster scored two fourth-place finishes while Bauer suffered a mechanical failure handing De Coster his third consecutive 500cc world championship.[2]

Håkan Andersson won the 250cc world championship to give Yamaha its first motocross world championship. Yamaha's new and innovative rear suspension with a single shock absorber made its debut at the third round in Belgium and was proven to be successful when Andersson won the overall victory.[6] The new suspension design would go on to revolutionize the sport.[6] Jim Pomeroy riding a privateer Bultaco, became the first American rider to win an overall victory in an FIM Motocross Grand Prix race when he won the season opening Spanish Grand Prix.[7] His victory also marked the first Grand Prix victory for the Bultaco factory.[8] Competitors from nine different manufacturers placed in the top ten of the 250cc championship final standings, reflecting the thriving vitality of the sport of motocross.

Round	Date	Grand Prix	Location	Race 1 Winner	Race 2 Winner	Overall Winner	Report
1	April 1	French Grand Prix	Tarare	Christer Hammargren	Roger De Coster	Gerrit Wolsink	Report
2	April 15	Austrian Grand Prix	Sittendorf	Jiri Stodulka	Jiri Stodulka	Jiri Stodulka	Report
3	May 20	Finnish Grand Prix	Ruskeasanta	Christer Hammargren	Roger De Coster	Jaak van Velthoven	Report
4	May 27	Italian Grand Prix	Pinerolo	Roger De Coster	Roger De Coster	Roger De Coster	Report
5	June 3	Czechoslovakian Grand Prix	Holice	Willy Bauer	Willy Bauer	Willy Bauer	Report
6	June 24	United States Grand Prix	Carlsbad	Willy Bauer	Willy Bauer	Willy Bauer	Report
7	July 15	West German Grand Prix	Bielstein	Willy Bauer	Roger De Coster	Roger De Coster	Report
8	August 5	Belgian Grand Prix	Namur	Willy Bauer	Willy Bauer	Willy Bauer	Report
9	August 12	Luxembourg Grand Prix	Ettelbruck	Åke Jonsson	Åke Jonsson	Åke Jonsson	Report
10	August 12	Dutch Grand Prix	Sint Anthonis	Åke Jonsson	Gerrit Wolsink	Åke Jonsson	Report

[5][9]

Round	Date	Grand Prix	Location	Race 1 Winner	Race 2 Winner	Overall Winner	Report
1	April 8	Spanish Grand Prix	Sabadell	Jim Pomeroy	Adolf Weil	Jim Pomeroy	Report
2	April 15	Italian Grand Prix	Serramazzoni	Heikki Mikkola	Pavel Rulev	Adolf Weil	Report
3	April 29	Belgian Grand Prix	Wuustwezel	Heikki Mikkola	Håkan Andersson	Håkan Andersson	Report
4	May 6	Swiss Grand Prix	Payerne	Håkan Andersson	Håkan Andersson	Håkan Andersson	Report
5	May 13	Polish Grand Prix	Szczecin	Håkan Andersson	Håkan Andersson	Håkan Andersson	Report
6	May 20	Yugoslavian Grand Prix	Orehova vas	Guennady Moisseev	Håkan Andersson	Guennady Moisseev	Report
7	June 17	French Grand Prix	Cassel	Adolf Weil	Håkan Andersson	Adolf Weil	Report
8	August 5	Finnish Grand Prix	Hyvinkää	Håkan Andersson	Håkan Andersson	Håkan Andersson	Report
9	August 12	Russian Grand Prix	Leningrad	Adolf Weil	Adolf Weil	Adolf Weil	Report
10	August 19	Swedish Grand Prix	Ulricehamn	Håkan Andersson	Håkan Andersson	Håkan Andersson	Report
11	August 26	Austrian Grand Prix	Launsdorf	Adolf Weil	Heikki Mikkola	Adolf Weil	Report

[10][11]