I am unable to find a manual for the LX 425 Toro lawn tractor. Have ordered 3-4 lower drive belts and all seem to be too small. Is there a manual on how to replace drive belts available

try this link
Toro LX Lawn Tractor Service Manual Page 2

Motion drive consists of two belts,
Engine to variable speed pulley 5/8 x 90-1/2
Variable speed to transmission 5/8 x 42

How to Replace Drive Belt in Toro LX500 Lawn Tractor eHow

MOST LAWN TRACTORS DO NOT HAVE A FUSE BOX. SEE IF THERE MAY BE A IN-LINE FUSE.

well I have a Lx 500 and the problem is that the bearings on the pulley shafts are wore out, makin the pulleys hard to turn or dragging heating up your belt. It heats up from the friction of the pulleys not free spinning like they should. next time you have the belt off check out the pulleys and see if they spin freely that will be the tale tell sign.

Jump onto www.toro.com and download the free service manual for your machine. Note down all the details on the ID plate on the mower, you will need it to find the correct manual......

Could be your coil. Might be bad or it went out of gap. Gap is .10

You can go to Toro.com and look at the lower left side for "Homeowner" or "commercial" parts. If you enter your model number you can get an owners manual online. I tried your LX425, but didn't come up. Maybe a different number?

For removing/replacing the deck belt, the general method is:

1. turn off engine, remove key and set parking brake
2. disengage blade by putting blade engage lever into off (disengaged) position
3. lower the cutting deck to the lowest position (closest to the ground)
4. relieve the belt tension (depending on the model, use a 3/8 inch ratchet set to tighten in the square hole of the idler bracket)
5. remove and replace the belt

NOTE: it's not necessary to completely remove the cutting deck.

Useful diagrams for removing the cutting deck, http://216.213.143.2/ProAuthor/ManProc.cfm?ManualID=425&ProcID=14794

For deck belt diagrams, http://216.213.143.2/ProAuthor/ManProc.cfm?ManualID=425&ProcID=14796

If the transmission drive belt needs to be replaced, several components must be removed and special tools (i.e. air/impact wrench) used in order to change the tractor's transmission drive belt. See an Authorized Toro Service Dealer to have your drive belt replaced.

you can check the idle pully to see if it is working,, spring could be stretched,,or you could need new belt, hope this help