Craftsman 917.287121 keeps throwing drive belt

[dart451]

I'm wondering if I should order an 89" belt...seems the 90" I have is too long?
...

[KE4AVB]

Actually it is likely the two v-idlers are Plastic/Nylon composite. If so the belt is probably bottoming out in the v-groove due to wear. At that what I find a lot with these pulleys.

[dart451]

Haven't thought about that at all! Thanks KE4AVB! Maybe a couple idler pulley changes

[dart451]

Ok, I checked the plastic pulleys...they seem to be just fine! In fact, the belt doesn't sink into them as much as some of the metal ones do on the mowing deck. Plus, the plastic pulley has a flat inside where the flat of the inside belt bevel rides on...it's not V'ed like I've seen some pulleys where a belt could eventually wear the belt into a V. So, I have ordered a Browning 1302520-3839 BELT RULE. ( Yes, they are quite expensive...don't know where I might get extensions for it though). I've removed the drive belt and will measure it when I get the Browning belt measure.

[38racing]

My supplier lists belts in size order with oem pages so if you want I could scan for something between 89 and 90. Just looked at 532125907 and my supplier says that it's 90 1/2.

[dart451]

My supplier lists belts in size order with oem pages so if you want I could scan for something between 89 and 90. Just looked at 532125907 and my supplier says that it's 90 1/2.

Ok, that would be great! It will take awhile for my belt measuring tool to get here. Perhaps I can find something that's closer to 89 or 90

[38racing]

I'm having the reverse problem on an old 36" husqvarna. Withe clutch in the belt stops but I still can't shift gears. If I shut the engine off then it shifts. Even though belt is not turning the transaxle pulley it appears to have just enough tension to affect shifting. Might be combined with an issue in the transaxle. I just ordered a 90" for it as ipl belt is 88 1/2. Although I'm (edit) NOT sure of belt size on it. I roll mine up the garage door jam to measure.

[Arkie]

For measuring belt lengths I use a cloth upholstery tape measure, cost about $3 and can find in wal mart sewing section.

They are about 120 inches long and can easily be used to measure the OD length of belts. Some of the cloth tapes are 1/2 wide and some are 1 inch wide.

I've started measuring the length of a used belt (that I'm replacing) then measure the length of a NEW replacement belt BEFORE ATTEMPTING installing. I've had to reject some new belts because they are not correct size as stated when purchased. ( expensive belts)

Really sucks time and money when a new expensive belt is installed and then find out it's wrong length after eq is operated and not even the correct length advertised by the manufacturer.

[dart451]

Well, I measured the belt I took off the mower and now I realize how easy it is to measure a belt! Used the string method and I get 89.5" for a 90" belt! So, the belt isn't stretched, in fact it's slightly short of what OEM prescribes! So, this is a mind boggler! I cannot see how the belt is jumping off, the belt retainers are all good, the tranny is bolted down securely and the tranny shaft doesn't appear to be loose. There is still the question of the plastic pulleys but I really don't see where the belt is sucking down into them! Think I will try an 89" belt and see how it goes...

[dart451]

I thought I'd close this post with this. I did buy an 89" belt and installed it. That fixed the problem! Now it moves perfectly...