The solution to winning hard seasons is to get the #2 bike by winning the challenges. The way you get the bike is by taking the challenges that have a photo card. If you complete these, you will have won the #2 bike. Although the game gives the impression that the longer the race, the better off you are in the possibility of winning, this is false. All hard arcade races, seasons, etc. should be set to only 2 laps. The races are short, but the racers gear themselves for a 2 lap race, which can be used to your advantage. Before you begin your arcade race or season, set the #2 bike up correctly. Go to "Settings" and use the following values.

Transmission: Set to only 2 notches
Brakes: Set to maximum
Handling: Set to maximum
Acceleration: Set to maximum
Once you have these settings, you will win every arcade race, and will come in first for seasons you have to race. If you place second in a couple of races, you will still win the season. All challenges from here on in become relatively easy.