The first opportunity I had to unlock this achievement came in Event 4 of the first series Naked Bikes: Middleweight as I started the game with the Triumph Street Triple
Naked Bikes: Under 700cc
Time Attack - Almeria GP Circuit
The target time for Gold is 1.47
I completed this on lap 3 of my first attempt using the stock Triumph Street Triple
I found better lines and the correct braking area with each lap and finally got a time in the mid 1.46 region
I had only just started the game and the only thing I had changed on the settings was to turn Auto Brake off, everything else was left at the default setting.
I am experienced at racers, so that may have made it easier for me, less experienced racers may prefer to come back to this when they have more experience, use an upgrade bike or chose one of the later events on a track their prefer.
As with any time trial event, track knowledge is key and that only comes with practice