My Craftsman riding mower (model 502.255040 ) jumps forward when brake\clutch is released. It will actually do a wheelie. I just got it from a friend so I don't have much history on it. It seems to run fine after the initial jump forward \ wheelie. No matter how slow I let the clutch out it still jumps. I tried adjusting the brake and clutch - which didn't help (but I'm not sure I'm adjusting them right). Any suggestions?