Recently brought my first bike a 2o12 yamaha ybr 125cc Ive noticed if i down change through a few gears without releasing the clutch sometimes it makes the bike go completley out of gear , sometimes it may of left me in a higher gear when i release the clutch other times ill be in no gear then when i rev it makes a horrible noise then goes into gear , also noticed when it does this when im stopped , i can press the gear down lever as many times as i want and if wont stop at the top like it does when your in first gear , if i slowly release the clutch at the first point of bite the chain pings and goes into gear