2001 mtd yard machine with all new belts and one new idler pulley..mower runs great but only moves very slow..whats wrong?

I had a 1999 yard machine that did the same thing i had to replace the transmission it was still working when i sold it this year

look under the mower and see if the drive belt has come off of any pulleys. sometimes they will have a stick get in there and the belt will come off and it wont move. also be sure it hasn't broke.

check the spring on the pulley to the drive belt it may be weak or missing

worn belt or weak spring on on the transmission pulley could be the cause

Check all pulleys for bad bearings by removing belt and they should turn freely without feeling any resistance or roughness, make sure idler pulley is not loose on shaft, check for alignment of belt (deck itself could have warped).

Here's a diagram, not a great copy, but it may help:


The spring hooks to the idler arm on the opposite end from where the pulley is mounted. The other end of the spring looks like it hooks to a raised tab on the deck, straight behind the left mower spindle. Hope this helps you, please rate my solution if so, thanks!

Yes it can be fixed. Try some basics first.
1) Check under belt drive cover for excess debris
2) Belt and Idler pulley condition
3) Control cable operation
a) rusted, frozen, broken, disconnected

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

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.

make sure the narrow side of the belt goes in the pulley; you may have the wrong belt; make sure all the pulleys for that belt are the same height , if one is higher than the others that may be the problem

I have the exact same model MTD tractor with same problem. It began when the bolt that extends through the idler arm assembly broke and subsequently damaged the pulley. Upon examination of the broken bolt, I found that the threaded end that extends below the deck is significantly smaller that the rest of the bolt. I got a larger bolt with the same size threads, bored out the hole through the deck and it made the whole idler assembly much stronger. the deck still has some vibration and some unusual belt harmonics, but it appears to be working. Compared to most other tractors of this size, this deck is very complicated.