newbe question time

[caretaker62]

hi folks as i said new to forum love it , here we go fzs 11,000 miles 2001,bike on stand 1st gear chain seems to jump about a bite is this the norm .tookof sprocket cover sprocket and shaft fine.old nut do i need to replace and if i do will a yamaha dealer do it .the gasket was shot do i need to replace if so whats it calledand can someone recommed a good spray cleaner for removing old thick sticky oil bike needs good clean im afussy git thanks again all your stars