Roughly the same but at lower rpm. originally I got 92 km at 8500 (max hp) but now I get 90 at about 7650.
Then aerodynamics comes into play. I can get more "downhill with the wind behind me". But top speed is useless for everyday use. Even if I could get 100 I don't have anywhere in my regular travels to do that. Uphill is much better and as I have hills around me... It is also better for occasional two-up.
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Acceleration from say 65 to 80 is much better. But I do have a flat spot at a steady 4500 and about 45 kph. Engine won't develop enough torque to get the torque tube to move and shift down. I just have to avoid that steady speed which I normally do, so I have no plan to change anything to fix that. Except maybe a bore-up to 120cc, just because I can.
Is your Forza 280 or 330cc? I have a mate with the 280 version who is using lighter weights. I could ask him. he hasn't complained so far.