How do u change the belt on a kuboto g 1900 deck

Jim, Double check to make sure you have correct belt for the deck and are installing it in the correct configuration as per manual or drawing on deck. Very few lawn tractors have deck belt adjustment, most do not, most deck belts have a spring loaded tensioner to take up the slack.
This could be some of your problem, the tensioner/idler pulley sometimes seize up and must be lubed up till they move freely, or your belt could be loose. Look in your manual or try google searching your make, model #, deck belt adjustment.
How to Change Riding Lawn Mower Deck Belt

Mower belt tensioner repair question to the Garage Gang

lawn mower deck belt routing Google Search

The one on the deck you will have to remove the deck. Flip it upside down and replace. There will be an idler wheel with a spring on it that allows you to release tension as you put the new on. The drive belt comes from the front of the motor and loops underneath to the cutting deck. There will be a point on the deck that you can get a little wiggle room to move it forward to get the belt on.

Dan, Mower deck belt diagram /replacement links below. "I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."

Riding Mower Deck Belt Diagram DIY
Riding Mower and Garden Tractor Belt Routing Diagrams
deck belt diagram craftsman riding mower Google Search

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.

there isn't such a thing... it's either a hydro (motion) belt or the deck drive belt. Dixie's also sometimes had 2 belts for the deck... the drive belt and the blade belt. your model number should be under the seat

see the video attached. lube the rollers bearing front+back . Test the drive belt motor for to loose or faulty belt, and fix it.
However if the problem persist, TIME to replace the old board deck.

God bless you

There is a spring attached to a tensioner that probably came unhooked while changing the belt. Higher deck settings push the deck backwards enough to spin the blades, the lower setting need the spring tensioner to take up the slack in the belt.

1) Lube the deck belt, in according with the instruction manual.
2) Lube the rollers bearing, with the i. manual
3) Test the input voltage motor, if there are the motor need repair
4) Test the output voltage board, for input voltage motor, if there are Not the board is faulty. God bless you

What pin code? I have never seen a pioneer tape deck that requires a security code.