I noticed that when I would rev my bike it would make a rattling sound. I looked closer and saw that the engine moves when I rev. The bolts in the back of the engine seem loose but they are really tight. The I noticed that the spot where the screw goes in is not securing the screw. Why did this happen? Is it ok to ride? All of the other bolts are on and ok. Can I continue to ride without worrying about the engine falling off?