My KFX 400 has ran good for so long. But, now there is a knock on the right side of the motor(while sitting on machine), up near the fan. You put your hand up to it and you can feel it. Then once I take my hand to the other side you can't feel it there. You can also hear it, its somewhat loud. It's just on that one side. It drives fine and there is no loss of power. I'm just concerned of what it could possibly be. You guys on here are great to help a youngster like me and I look forward to your replys! Thanks so much!