Les, forgive me for suggesting it, but if it’s on the driver/off side, are you sure you are going the right way as it is a left hand thread on that side, and will need to go clockwise to undo. Easy to forget.

Doug
2011 Plus 4 in Rich Maroon

1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900