Easiest way I have found is to open one bleeder and squeze and hold the brake lever,tighten bleeder than release brakes,it pushes the air out instead of compressing it.
If you rev the bike up does it take a while to return yo idle? If it does,check for a air leak. Spray carb cleaner around the carbs and reeds with the bike running and see if the motor idels up.
Is the bearing comming in contact with the weld when you tighter the nut?Pull the crank back out and tighten the nut,look to see if the bearing touches the weld.Or the weld hitting the cases putting the bearing in a bind.