Its possible that the battery has enough power to turn the engine but not fast enough to start it.. are you getting a spark at the plug and if so is it nice n healthy?..ie a nice fat spark that cracks and can jump 2-3 mm?

Is it the original battery?

I have spent hours trying to sort a non starting ccmr30 and ttr 600 only to replace the battery as a last resort and cured the issue.