I have two gpz900/zx900 ninjas. The bike requires a cooling fan switch and a resistor modification to the heat sensor. One will keep the bike form acctually overheading the other just lies to you about the heat. If you want to keep riding on hot days you have to install a larger oil cooler and remove the fairing arount the lower part of the engine, or turn the fan switch on when riding in traffic and do not rev the engine. I replaced the zx900 with the 1886 zx1000 engine. It came with a larger Radiator which did not fit the zx900 frame. I bought a UK radiator that fits without the lower fairing. It runs great without overheating because of the larger radiator and the lighter metals used in compared to the 1984 zx900. It puts out 125 hp and will take the bike to 157mph, 160 on a cool day. Mikuni carbs replaced zx900 factory carbs.