To change the cam chain tensioner on a Honda CB400F2, it typically does not require splitting the crankcases. The cam chain tensioner can usually be accessed and replaced without the need for major engine disassembly.
It is always recommended to consult the service manual or seek assistance from a qualified mechanic who is familiar with the Honda CB400F2 to ensure the proper procedure is followed.
By following the appropriate service manual or seeking professional guidance, you can safely replace the cam chain tensioner on your Honda CB400F2 without the need to split the crankcases.