I put a new drivw belt and pully on my murrary 43 inch riding mower, but now I can't keep the belt on it well rur for a lap or two then fall off. What do I need to do?:confused:

There should be a tensioner pulley for that and maybe you looped that incorrectly.

21 is correct unless you aren't sure you used a OEM correct belt. Tell us exactly why you needed to replace the belt, what was the old one doing? Where did you get this belt? http://www.best-price.com/product/offers/sid/877345961/q/riding+mower+belt/placeID/