I have a zero turn radius mower it runs blades spin machine will not move. Is there a pulley tensioner to adjust?

Hope this helps. Serpentine Blade Drive Belt
1 Lower the mower deck to its lowest position.
2 Route the serpentine blade drive belt (part number 6109) onto the V-pulleys located on the mower deck. One double pulley is located at the front of the deck near the center. The other two pulleys are located near each side of the deck. Route the belt around the outside -- the side toward the outer edge of the mower deck -- of each pulley. For the double pulley near the front of the deck, route the belt around the lower pulley (part number 6058) only. If pulleys are fitted with belt guards, work the belt in between the pulley and shield.
3 Push the idler pulley toward the center of the deck with your hand. The idler pulley (part number 6059) is the fourth pulley on the deck and is located near the rear of the deck. It is the only movable pulley on the deck. Wrap the belt around the side of the pulley nearest the edge of the deck. Release the idler pulley to place tension on the belt. No adjustment is necessary because the serpentine idler spring (part number 6065), located on the idler pulley, adjusts the belt to the correct tension.

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.

Remove blade drive belt. turn each blade by hand. Sounds as if you have bearing problems. Each spindle has an upper and lower bearing of the same size. They are notorious for going out! You can get them at most any auto parts store. Also check the tensioner pulley bearing. They go out quite often. As for the jerking, make sure the two drive disengage rods are fully in. Check tension on drive belt and belt. These belts get worn quickly. Be sure to blow the trash and dirt from your mower after each use. Especially the Hydraulic motors and the mower deck. This will save you lots of trouble. If you wash the mower, be sure and run the blades and Hrdroes to get water dried from bearings and pulleys and belts.

check your pulleys to make sure they haven't split as this does happen. Adjust the belt tensioner to tighten the belt when you engage the clutch to drive the mower. You should be able to see the belt tensioner by dropping the cutting deck to its lowest point and looking underneath the mower to see which pulley actually puts the tension on the belt to make it drive. there is no need to start the mower to find which pulley needs to be adjusted, it should be obvious when you look at the belt and the pulleys.
Hope this helps you

check that the drive pulley to the hydraulic unit is still fixed to he shaft and has not got loose and just turning but not driving the pump shaft. Other than that you may have to check out the pump pressure of the drive unit.

sounds like you smoked a belt check your blade tensioner belt, possibly an idler pulley bearing or your belt jumped off pulley, not getting right tension on belt for blade

This is a belt adjustment problem. You machines belt has either broken, or is loose to the point where it won't engage the blades at all, or has just slipped off the pulley. I believe the belts are on top of the deck covered by removable covers that are bolted to the deck. Check and see. GOOD LUCK.

I am not sure what type of blade engagement mechanism you have (ex. clutch, tensioner/idler pulley, etc...) but make sure that the blades can spin freely with the belt taken off of their pulleys. It could very well be that one of the pulley bearings is seized.

Another possibility, is a broken spring or a tight/ rusted idler pivot arm.
with the engine off & the deck down, engage the pto & pull on the belt to see which pulley is the tensioner

drop the deck and check all of the moving parts. you have a part that is frozen up, maybe a single blade pulley wheel which is causing this.