This is a picture of the KZ-900, it's used in season one and season two.
The KZ-1000C1 was used from season 3. It has a bigger windscreen and front fender, smaller pursuit lights and other little changes.
They used the same trailer for season 3 as they did in the first two seasons. The bikes on the trailers were KZ-900 and those had the big pursuit lights and other windscreen. Because the difference would be visible, they removed the KZ900 windscreen and put a KZ1000C1 windscreen on the bikes but they forgot to replace the pursuit lights (they are bigger on the KZ900) and the metal frame below the headlight (missing on the KZ900).
Erik Estrada owns one of the KZ-1000C1 bikes which was used in the series. Note that the engine was taken out.