me and my brother both have 350 raptors. they both have some little problems. mine starts up fine but my brother's goes "CLANGK! CLANGK! CLANGK! CLANGK!" when he trys to start it. it did it ever sense he got it. he got it used. it did make that sound then start up, but now it wont even start up. the oil is changed and it has good gas and it still does it. when he changed to oil, it had metal flakes in it. what could be wrong with it?