This is a common problem with this mold (Copied from Transformers Wiki "There's an automorph-like feature in his right leg. Pulling up on the gas tank causes his rubber handlebars to be dislodged and moved to the side. Do NOT unhinge the handlebars manually. Moving the handlebars manually creates stress points in the hinges that connect them to the gas tank, resulting in many reported instances of broken hinges. Unfortunately, many have found that the nubs that hold the handlebars in place in bike mode are too strong, and even using the automorph as intended causes the hinges to quickly break. Cutting the nubs off has been the only consistent fix to prevent breakage")

I had this same thing happen to me 5 mins after opening the box....All I used was a bit of 5min epoxy, make sure you sand the damaged parts or they wont bond properly, I suggest you fill the original hole in. Don"t use the original pins, If you have some spare small thin screws like the ones you get when you pull a toy or Transformer apart.Use these instead of the pins. Also cut of the small knobs, theses are the problem, you loose the automorph though..