MotoGP 1 (PS2, 2000), an answer lost in time

I know this is out of left field, but I recently picked up this game again and wanted to finish it for sentimental reasons. However, challenge 50 is proving tricky - the bronze is easy enough, winning on each circuit with each of the best 3 bikes, but I can not win the silver or gold, regardless of what I try.Given the help line for such a thing closed only a dozen or so years ago, and no detailed guide seems to exist anymore, I wondered if anyone here could remember how...?
Submitted September 02, 2018 at 11:16AM by Me_h https://www.reddit.com/r/motogp/comments/9cb3bi/motogp_1_ps2_2000_an_answer_lost_in_time/?utm_source=ifttt