Thud sound on engine start/off

[YN89]

Hey guys took out my rappy today and noticed when the engine would be running hot every time I start her up a thud sound would come out near the clutch area same as shut off.. Is this normal or am I in trouble?? Also when i arrived home once I unloaded my bike off the trailer it woudent start it's just cranking over, over,over, what's happening to my quad????