The plunger of the chain tensioner is designed so that the ratchet mechanism
only allows the plunger to fly out and does not allow it to be pushed inward. Move the stopper plate, release the ratchet mechanism,
push in the plunger, and then loosen the timing chain.
CAUTION:
Removal of the chain tensioner while the timing chain is still under tension
could cause the chain tensioner to fly out, resulting in injury, so be sure to relax the timing chain tension.