this will sound daft and sarcastic but is not...
Is it clean and lubed?? lots of chain lube now just makes the chain stiff and dry (but it doesnt fling!) We see REALLY dry chains all the time and they just need a good clean and de-grease and re-oiling with something nice and slippery.
Get it on the paddock stand and check for tight spots.
.... and check the hub!!!!
