grinding didn't sound good [as in serious but not clutch sort of thing], now we need [want] to know what you found?, good it's sorted though. Had one of those brand new [MX250B 1975] one of the best most solid & reliable bikes i ever had. New piston every so often [original yamaha pistons in those were a 'very' solid piston & meaty around the inside of the cutaway to give it strength.