My cub cadet ztr 50 keeps breaking drive belts the 1st after 130 hours and now after 4 hours

My first guess is the belt is not properly routed through all the pulleys and past the belt keepers. Please check everything twice against the belt diagram in your operator's manual.

Changing the Blade Drive Belts:
a.Set the parking brake. Remove ignition key and both spark plug caps.
b.Unscrew the wing nuts from the deck covers and remove both covers.
c.Using a 3/8" socket breaker bar or socket ratchet insert the drive end into the 3/8" square opening in the lower idler arm assembly and push the idler arm counterclockwise. While holding the idler arm back, loosen the blade drive belt from the pulley and slide the belt away from the pulley.
d.Remove tension of the PTO belt by moving the belt tensioning rod. Loosen the belt retaining bolt.
e.Pull the tensioner pulley away from the belt and remove the PTO belt then remove the blade drive belt.
f.Reverse the process to install the belt.

check all the blade spindles for seized bearings. also check the pulley alignment, those issues can cause premature belt failure. Also proper tension can give you consistent long term use.

Link to see video of the Fix for cubcadet deck belt coming off can be viewed here: http://www.youtube.com/watch?v=Pd4nYovcnvY

check that the idler pulley is assembled on the belt properly as the belt is not to run against itself at any time

siezed pully bering check to see if there is a grease fitting if not get PB BLASTER best stuf ever made to loosen up tough stuf

sounds like possibly burrs on pully, or pully depth is incorrect, causing belt to jump.

mostly all lawn equipment gear axles & engines run on sae 30 weight oil & it should be 1/2 to 3/4 full unless told other wise

I have a cub cadet zero turn z force 48 yesterday i was cutting lawn and i heard a clink, the mower stopped, i was ablet o start the mower again but when i pulled the pto knob to engage the blades the mower turns off by its self, when the pto lever is pulled up i can restart the mower what is causing this and how do i fix it

check the alignment of the ideler pully to make sure it is even withe the drive pulleys. if not in line it will cause the belt to break. There is a spacer that is on the idler that should be on top and not on the bottom of the pully.