My belt for the deck is very loose,when I engage the deck it stalls. I replaced the belt, but it is still very loose.I did have a broken belt keeper, replaced it, does belt tighten when deck engages? Just seems like belt should be a lot tighter.

Hi,
Easier to answer if model number is supplied. On most WeedEater brand mowers the belt tensions upon engagement. Exceptions are ones with electric PTO.
Peace,
Clarke