I went to adjust my valves, located the TDC mark on crank but there was no index mark on the crankcase. I could not get any slack in the rockers…even when I rotated 360 degrees…. Many times. This is for the 20 hour valve check…and I have the 4 year warranty so I am not so keen in taking a chance on the valves. Any suggestions? This is an 05 Foreman.