Load up Single Event > Skill > Track: India - Tamul Nada 02 > Event Settings: Default
Repeat this event until each bike is 15. You'll score ~15,000 fame per good run every 35-40 seconds.
I suggest going through the DLC before doing these. I think some events use base game bikes. You can also cut the grind in half by purchasing fame boosters. At the time of writing you could purchase 500 for $11.99.