I changed the drive belt and small idler pulley

Safety and Preparation Serious injury can occur if the engine or mower blades accidentally start while you are working with lawn tractors. To prevent this, drive the Murray lawn tractor onto a flat work surface and disengage the mowing deck cutting blades. Engage the parking brake to keep the mower from moving; chock the wheels with a wooden block or brick. Adjust the mowing deck to the lowest position. Turn off the engine and remove the key from the ignition. While not necessary, you may even wish to disconnect the spark plug wire from the spark plug. Mowing Deck Removal You must remove the mowing deck on a Murray lawn tractor to gain access to the belts. Remove the adjustment rod hairpins, followed by the adjustment rod pins from the front left and right sides of the mowing deck. At the rear on the left and right sides, pull out the retaining hairpins and slide the mowing deck suspension links from the adjuster plates to separate the rear mowing deck from the frame. Remove the blade control rod stud, including the hairpin and washer, from the top of the blade control lever shift linkage at the left rear of the deck. Remove the front hanger rod, including the hairpin and flat washer that hold the rod in place. Loosen the belt guide retaining bolts with a socket wrench and remove the engine stack pulley belt so you can slide the mower deck out from under the tractor Transmission Drive Belt Installation Slide the new transmission drive belt between the engine stack pulley belt guides, over the belt guide plate and under the engine stack pulley. Fit the transmission drive belt around the top engine stack pulley. Push the free end of the transmission drive belt up through the transmission shifter hole in the lawn tractor floorboard. Slip the transmission drive belt loop over the transmission shifter. Pull the transmission drive belt down through the transmission shifter hole. Fit the transmission drive belt around the transmission drive pulley and tighten the transmission drive pulley belt guide retaining bolts to hold it in place. Fit the transmission drive belt flat side around the idler pulley. Slide the idler pulley onto the idler pulley stud while holding the belt in place. Tighten the transmission idler pulley retaining nut with a socket wrench to secure the idler pulley to the idler pulley stud. Mowing Deck Drive Belt Installation Pull back on the right side mowing deck mandrel pulley spring-tensioned belt retainer. Guide the new mowing deck drive belt around the right side mandrel pulley and release the belt retainer. Pull the drive belt spring-tensioned retainer away from the mowing deck idler pulley, guiding the deck drive belt around the idler pulley. Fit the mowing deck drive belt around the left side mandrel pulley and under the rear mowing deck cross link rod between the right and left side mandrel pulley. Slide the mowing deck under the right side lawn tractor frame, reconnecting the deck to the frame in reverse order of removal. Engage and disengage the mower deck while driving the mower to test the belt for proper operation.

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.

lift the front of the tractor up at least 3 feet and lower the mow deck to give you clearance. push the clutch pedal and lock it down to release belt tension. remove the mower belt from the engine pulley only. remove the trans belt from the idlers about midway back then from the trans pulley & finally from the engine pulley. put the new belt around the engine shaft above the mower drive pulley but not on the drive pulley then around the trans pulley. now you can put it on the drive pulley and finally on the idlers. make sure you have it under all the various keepers or the belt will shred in like 10 minutes. release the clutch pedal & check the belt again to ensure it is in the correct place. replace the mower drive belt & ensure that didn't come off other pulleys in the process. lower the front of the tractor and test

If you don't have your manual, this might be for yours (you didn't list complete model number)
http://www.managemylife.com/mmh/owner_manuals/10259/TROYBILT-Lawn,-Tractor-L0401081?brand_name_search=14AZ809H063+TROYBILT
See the part about changing drive belt and adjusting. If you got it around idler pulleys wrong, it might not lelt the clutch go far enough to apply the break.

This is actually pretty simple:

Remove Pto guard on mower deck

Stand mower up on back stands

Pull the friction disc away from the drive disc

slip new belt in between the friction disc and drive disc pushing all the way through

release friction disc allowing to come back in contact with drive disc

loop belt around engine pulley

let mower back down

route belt around mower pulley

loosen guides on idler pulley

route belt through idler pulley

with engine off move pto lever to tighten mower belt

adjust guides on idler pulley allowing 1/8" from belt

tighten bolt on idler pulley

release pto tension

install mower pto guard

and you should be ready to mow

The front belt should be a 954-0280A, rear 954-0370. When you go to higher gears, the front belt should be getting tighter as the vari-speed pulley is moving further back. Remove the shift plate, put the transmission in neutral. Start the engine, put speed selector in highest gear and slowly let out on the clutch. You should be able to see what the problem is. It will do everything the same as if were in gear, except move. Make sure you have the correct belts.

my murray riding mower wont pull when i put in gear i dont have a clue what to do,it doesnt seem like its going in gear

I have seen this problem on other tractors. It is caused by a loose or sticking drive belt between the engine drive pulley and the transmission. There is an idler pulley between them that is spring loaded to keep the belt tight. If the pulley bearings froze so the pulley doesn't spin, or if rust or a broken spring prevents the pulley from swinging over enough to keep the belt tight it would cause the problem.