I have an MTD Yard Machine lawn tractor (model 13AN601H729, 20hp, 46in deck ) that was purchased new in August of 2006 from Home Depot. The deck belt keeps getting shredded and the pulley idler bracket keeps getting bent forward and has even snapped in half once so far.
The deck belt has been replaced 4 or 5 times, the idler pulley has been replaced once and the pulley idler arm has been repaired 3 times including having to weld it back together after if snapped in half.
The belt is going to be replaced for the 5th or 6th time as well as another repair for the pulley idler bracket that keeps bending toward the front of the deck. This seems to be a common problem with numerous MTD tractors! Why haven't they been recalled yet as factory defects?
Has anyone found a perminent solution for this problem yet (other than purchasing a John Deere which is the ONLY mower/tractor left which has not been bought out by the notorious MTD company)?
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.
I have the exact same mower and problem. I removed the deck this weekend to evaluate, and noticed the left hand idler was tilted down. Since this idler is the one that takes the pull from the motor pulley, I decided to straighten the idler bracket, so I removed it. I decided to lube the big shoulder bolt that anchors the LH idler bracket to the deck (while I had the bracket out) and found it was seized to the bracket. I believe this is contributing to the problem as well, as the bracket is supposed to move (with spring tension) to absorb shock loads on the outside face of the belt (which is where I am seeing the first signs of wear). After straightening the pulley bracket, the cut is better and the belt lasted through both the front and back yards, though showing wear on the outer face of the belt). I will be replacing BOTH idler brackets and shoulder bolts shortly. No provisions are made for lubing then short of taking them out. I am considering adding a zerk fitting to the trunion tube on each idler bracket.
My MTD has lasted 13 years with minor repair,I would suggest trying a belt that is 1 inch longer,also there is 2 deck adjustment's were the rear of the deck imounted with pins try going either up or down 1 hole tryup first.hope this help's
March 14, 2011, I have exact same model with same problem. I have not yet found a solution. I tried a thicker belt, but it just flipped over and shredded after about two hours use. I have read others suggesting the height difference between the motor pulley and the mower pulley is too great, thus causing the problem. I use with deck in high position (6) only, but belt still shreds. One contributor said he replaced a idler pulley shoulder bolt with a regular bolt. NOTE: a shoulder bolt is designed with smaller treads to avoid overtightening and binding pulley. Since no other parts have broken yet on my mower, that does not sound like a solution. The belt does not seem to be happy bending in so many directions. Notice that there are no problems with the other two belts One to turn middle and right cutting blades and one drive belt. I wonder if the twin blade - 42" deck is any better? Frankly, the belt on that model has even more turns. I hope someone has found a soultion that they will share.
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I am having the same problem with my MTD and the same model #. The angle of the belt coming from the engine pulley to the idler pulley I way to steep. My belt is being shredded by the idler pulley. So far, no damage has occurred to the idler pulley, it looks as though that could happen in the future if I was to keep using it. As of right now I'm thinking of extending the bushing for the engine pulley to lower the pulley and thereby lessening the angle. Will also have to rerig the belt guard bars also. This is the only solution I can see for the fix. Hope that will solve my problem.
Terrible design by MTD.
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The solution to this problem is the strength of the stem bolts holding the idler brackets. The stock setup is a 5/8" x 2.515" x 3/8" shoulder bolt, which breaks off pretty easily. Fastenal sells a 5/8" x 2.5" x 1/2" shoulder bolt of a much harder steel and all you need to do is drill out the mounting hole in the deck to 1/2" and insert the new, stronger bolt. I installed a zerk as well, which seems to keep it from getting hot and binding on the bracket bolt tube.
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