I go this 125cc china engine for 50 bucks and it was in pieces. It had a broken sator pick up from the chain coming off and snaping it off the sator plate. seemed that engine was fixable. So im in the process of putting it all back together and apon taking the sator off i noticed this spring that supposed to keep tension on the cam chain tensioner was off the tensioner arm. So i have putnit back on the tensioner arm but it dosnt seem to be a very reliable cam chain tensioner set up, surely this spring just sitting on the cam chain tensioner arm isn't how it is supposed to be? Is there a missing part to secure the sping to the arm or is it just supposed to sit on it like in the picture.