The bike races are the most fun missions in the game -- A few hints......
Buy or steal a real fast bike...Exprement around with a few of the bikes, and you will see what I mean.....With a fast bike, you can jump ahead of the others right at the start, and stay in the lead...If you mess up and lose the lead, you CAN catch up..And if nessessary, punch the other riders off their bikes..
On races Involving going around the Lighthouse, the other riders will CHEAT and take the shortcut form the path to the beach, so you need to do that also...Otherwise, you'll be following the arrows around the Lighthouse in 1st place, and all of a sudden you have lost...What happened ?? Well, they cheated and took the shortcut to beat you....
You just have to be smarter than the average Bear......