common newbie mistake is overtightening the valve cover bolts. they strip very easily. Valve inspections are easy, just remove the tank/airbox/carbs or EFI then the valve cover (rubber gasket should be reuseable). Check with a shop manual for locating TDC and squeeze that gauge betw the cams and shims. I'm not sure if F3 has manual or automatic cam chain tensioner.
get a shop manual before working on your bike.