and tire pressure makes a big difference. I sometimes drop pressure if I am going to be on long stretches of dirt road, even with a more aggressive tire. on pavement if the front is low it will have a tendency to oversteer and fall into corners, even with street tires. I have 2 sets of wheels too. one set with TKCs the other with road tires. BTW, Ninja wheels fit, and are relatively cheap. rotors vary though & may need to be changed
if I'm answering your question I assume the basic points have been addressed, such as: did you do a compression test? is it still on fire?