While these karts may be based on real karts in my mind that's visual only. Both the acceleration and sound is off. I drove 100CC direct drive karts for a while and they took off like a tornado even out of tight hairpins and sounded much better than the GT5 karts do. Karts with slipper clutches don't sound all bogged down like the GT5 karts do. The throttle response on the 100's is bad enough, the 125 is terrible and they sound as if they are really struggling until they get near the very top of the rev range.
A shifter would not have been too much. It's what I was expecting with the 125 but once again, PD has dropped the ball.
Yes they are still fun to drive but nothing like the real thing as far as throttle response and sound goes.