Yx140 timing issue?
 

Hi guys, I’m not too familiar with these 4 stroke engines lol
I’ve re set the timing on my yx140 by lining up the flywheel mark with the one on the cam sprocket, they line up fine but my only issue is I have to hold the flywheel in place by hand as it wants to jump back an inch or so, is it meant to stay in the same position or does it mean my cam chain has stretched with it jumping back?