shot in the dark - are your motor mounts in good shape ? An engine moving around won't be good for that mower drive belt...

Think they are, but will check them.

Do you see any smoke or hear the engine or deck sound change before the breakage. Only guess I would have would be the idler pulley bearing, but it the idler pulley stops you would surely hear squeal and see smoke along with engine RPM change. Belt Routed right? Right???

No - there is no sound or visual change. The only sound change is after the belt breaks the noise associated with the blades turning stops and it sounds just like it would if the mower was not running. The belt is routed correctly both according to the dealer (who has installed it on several occasions) and also based on Cub Cadet's manual.

A pulley to pulley belt drive is pretty straight forward and a good quality belt is very tough. So for it to break in that short time something obvious must be going on. Check the edges of both belt pulleys (sheaves) for sharp edges that would cut through. Get under there by jacking up the front of the mower or driving it up on a couple of car ramps; visually make certain the pulleys are aligned with each other. Physically try to move the pulley and shaft from side to side in all directions and look for play. As was mentioned, make certain the idler is turning freely, and make sure the belt is not rubbing against a sharp edge of the frame or a belt guard. Something obvious should jump out at you....

Actually, thinking about it, the alignment of the pulleys shouldn't matter too much since they generally go out of alignment when you raise the deck up. Still, it sounds to me like the belt is being cut by something...

When I have it running and look at the belt everything looks OK. There is no vibration and it looks like it is running smoothly. When I examined the last belt that broke it looked burned on the outside. Could it have flipped over so that the outside was running against the pulleys? What would cause that?

I look at it this way. If what you are seeing is that the belt snaps in half, it is being grabbed and held- like between a pulley and guard or belt guide. It would be good to know for sure this is what is happening. It sounds like you are mowing lightly as not to aggravate the situation- so is it safe to assume that the deck is not being overloaded, that the blades are not worn/ dull/ out of balance and trapping clumps of grass between the blade edge and deck? IF the spindle bearings and bearings in the mule pulleys are running cool and smooth- then look at what keeps the tension on the belt. Parts that pivot have to do so freely, shouldn't be worn at the pivot point and if acceptable- then replace the tension springs. Let us know what you find, what deck you are running, what belt you are using

IMO belt burned/worn on the outside means idler pulley problem (burnt belt means something is stopping, slowing down, or alowing idler pulley movement). It is the only thing that touches the outside of the belt unless you got belt pulley retainer rubbing (rod sticking down to hold the belt around the pulley when tension is releaved when the deck is taken in and out of use) I would also check idler pulley bracket and as mentioned spring and hardware.

The deck is a Model 46 LT Deck 300190 w/ SN 469896. I have used 2 different belts with the same result. I have used the manufacturer' rec 954-3055A and the dealer rec 954-3068.

You mentioned the last belt has some burning on the outside, but it isn't clear if the belt split and had broken in one spot- more like it was cut or if it shreds itself into oblivion.

The belt was burned on the entire length on the outside. It broke in one spot with about 3 inches of fraying on each side of the break - otherwise it looked fine.

Burned the entire length on the outside tells us the belt either rolled or was dragged across a dead flat idler or was routed where it had contact w/ something. So, it the belt had rolled and then gotten caught between a pulley and a guide- could be a plausible explanation. Was there any roundness on the top belt edges? Any burning on the sides at all? Is there potential for it to be caught on something running it's normal path? When the belt breaks, does it catch itself on something or does it simply toss the belt? In short what do find after it happens? Think of this like a crime scene and you're Columbo or the CSI guy....

OK, I have examined the broken belt again and this is what I observe. The V portion that is supposed to be touching the pulleys looks good. Not really any sign of wear. The outside portion has all of it's markings worn off. On either side of the break the outside looks burned for about 18 inches on each side of the break. For about 3 inches on each side of the break the belt is coming apart (frayed)on the outside. The edges of the belt while not sharp, do not look particularly worn or rounded. No burning on the sides. The normal path looks good and it should not be touching anything. The only thing I can see that appears abnormal is the bracket which holds one of the pulleys where the belt changes direction is bent from vertical by maybe 2 degrees. When running the belt looks fine and there is no vibration. When the belt breaks it does not catch it is thrown to the ground under the mower. My best guess at this point is the belt rolled over, but why would it do this? Any other ideas?

Cub's mule pulley systems can be finicky. I've had a couple with issues, but it's been a while. Your's has the V style front pulleys rather than flat? If you took the burned area and folded it over the clutch- that was the last metal it saw. Now, look for any nick on an edge and try and locate where that was on the path. That might tell what held the belt. A tensioner that has excessive slop could be the culprit. I do know as far as spring tension- it has to be right. I think there is about a 1/2 inch difference between the two belts used and the cut is slightly different. You will have to be the judge that pulleys are running smooth and cool and excessive slop does not exist. My recommendation when installing belts on these is also to condition the belt by running them for 15 minutes w/o load or very minimal load. Also, think like the belt. Follow the loaded side of the belt and think what way the twist would be more natural as it came off the clutch to the mule pulley. You may want to put the seat switch in a test mode so you can just plain sit and watch what is happening from below. Have one of those digital laser thermometers? It is a quick and easy way to tell if there a bearing working against you.

Thanks Tomplum for the suggestions. Please excuse my ignorance, but which pulley is the mule pulley. I have the pulley/clutch on the front of the engine, two pulleys that change the direction from vertical off the front of the engine to horizontal to go back to the mower and back to vertical, a pulley at the top of the spindle that connects to a pulley to power the belt that turns the blades. Wish I had a laser thermometer for all sorts of things, but I don't. Last year the dealer changed out the pulley at the top of the spindle because the bearings were bad. I will try your suggestion of putting the burn portion over the clutch tomorrow and see what I see. Are you suggesting the belt rolled over because it caught on something hence the nick I am looking for? I am just wondering what would cause a belt to roll?

The mule pulleys are the two below the clutch. The likely scenario is that the belt had rolled and grabbed something which held the belt and of course the clutch keeps trying to drive the belt that won't turn and burns it into toast. So, the question at hand is what and why. Is whatever grabs the belt able to do so due to a weak tension spring or worn tensioner arm that won't allow the belt to keep proper tension- causing the belt to get ahead of itself and allowing the belt to roll? This reiterates the need for a proper belt, proper installation and proper conditioning as there is lots going on in your system. Or something just bent /worn and affecting the belt in a different way? After you check it out and get a new belt on- I'm completely serious to think like your belt as you install and run it up. You see an area with lots of "wow and flutter" - think why...

With mule drives where the crankshaft is horizontal and the belt changes direction 90 degrees to the deck or snowblower there must be a twist in the belt (on both sides) between the PTO clutch and the mule pulleys. The twist can be to the IN or to the OUT but only one way is correct for the specific application. I've seen the twist applied bassackwards way and belts last a VERY, VERY short time.

This might be the OP's problem. The OP might have to get a magnifying glass and peruse the correct service lit for his.her Cub to make sure the belt has the correct twist.

In my experience when there is a mule drive ONLY the correct OEM belt installed CORRECTLY will survive.

Thanks for the info on the mule pulleys. Is there a way to determine if the spring holding the belt tight has the right tension? I can't find anything that would grab the belt.

I will check the literature for the correct twist. I did not know there is a difference. I assume the dealer would know and this last belt that broke was installed by the dealer.

I checked the instructions from Cub and this is all it states:
"Twist the PTO belt 1/4 turn to engage the narrow side of the belt into the grooves of the two tractor front lower pulleys." It does not state nor do the drawings show whether the 1/4 twist should be either inside or outside.

You may find a description on which way the twist runs in the manual like lurker says. The way to think about a belt set up, especially with one that is a bit more complex- is that the path has somewhat a push pull effect. One can visualize that a working blade spindle has more drag than a free wheeling idler pulley. Tension is important because of this. The direction of twist off the clutch may not be real important on yours, or it could make a significant difference. Belt tension may vary due to deck height as travel distance is not constant. The belt length doesn't change so the tensioner system makes up for that and its job is to ensure push equals pull more or less. Thinking like this after you have done your due diligence on verifying the condition and alignment of the components - will correct the problem.

It is amazing that the dealer wasn't able to figure this out.

"I assume the dealer would know and this last belt that broke was installed by the dealer"

How long did that belt last and what do we know about A-S-S-U-M-E ?

Get the service lit for your tractor and a magnifying glass or Optivisor and check every picture for the correct twist.

A Cub dealer that applies itself to the situation would be great. The OP noted that the dealer installed a belt that wasn't spec'd for the machine. That in itself isn't a big confidence builder. Maybe that was their attempt to correct the problem. There may be a bulletin on this. It would be great to have their insight into the problem.

So today I did maintenance on a 2166. It had G deck which is different. It occurred to me on this one, that it would be possible to install the front deck support inverted. On this one, the twist came off like you would roll the top of the belt towards the front.

Thanks for all the input. In to answer some questions that have been posed I will go into a little more history. I bought the tractor used in 2008. I had no problems until spring of 2010 when I was mowing grass that was about a foot high and the belt broke. The dealer thought the high grass not fully discharging built up until it broke the belt. He replaced it with the non spec belt because he said it fit better on my tractor. That belt lasted about 4 hours of mowing and broke when I was mowing normal height grass. I looked up the specs and got him to put on the correct belt which lasted about 2 hours of mowing and broke in the spring of 2011. As I recall the dealer found the pulley on top of the spindle had some bad bearings and replace the pulley and the spindle and the belt, but because of the drought I did very little mowing over the summer - maybe one in half or two hours. In November, 2011, as I was doing the last mowing for the year the belt broke. The dealer went through the system said he could find nothing wrong and replaced the belt. I completed the mowing and started keeping a record of how long I actually mowed. So in November I mowed 32 min on the belt and then when I went to do my first mowing of the year I mowed 10 min before it broke. Again the dealer has replaced it and found nothing wrong. He and I mowed an area next to the dealer and he observed my technique and the tractor performed flawlessly. I brought it home and completed the first mowing, so I have a little over an hour on this belt. I have my fingers crossed.

Based on what I can see in the Cub literature I tend to think the twist does not matter on this mower. From what has been said here, about the only thing that would roll the belt is it catching on something or the tension on the spring being too light. Am I correct?

If you can, stop going to the dealer and do it your self. You have a vested interest in this and he only has a $50 bill and a tech that doesn't really care as much as you do.

Find and purchase the repair manuals (Not the operating manual) for your machine then using your new found expertise and knowledge-
I would replace the belt, drive the machine to a safe area to use the deck for five minutes. Engage the deck and wait for 5 minutes (for it to heat up) then, SHUT IT OFF and using an infrared thermometer like the one in the link,
check all components for unreasonable temps.
Belts are far better than they were even ten years ago. What you are experiencing is / should be easy to find and correct. I would put money on a twist or wrong belt or some such obvious issue. Why? because I had the same thing on a Wheel Horse around 1978 or so. Mine was twisted and shoulda been flat - D'oh!

Here is a link that might be useful: Ryobi Thermometer

txmat

A single picture is worth a thousand words. Can you take several pictures of your belt routing (top view, side view, front view). Maybe we can see something instead of talking about it.

Also, is there another Cub Cadet dealer in your area. If there is, I would take it to him and see what he can do for you.

But post some pictures here. You got me curious.

I was taking a look at my buddy's '62 International that he was working on tonight. He's been wrenching at the equipment dealership for the last 40 years.

I couldn't help notice that it had mule pulleys, so I asked him about the belt breaking and proper twist question.

He said that the belts are always twisted the same way. Looking from the front, the belt section that goes down on the left always twists clockwise and the belt section that goes down on the right always twists counter-clockwise.

One thing you might try is to make sure your mower deck is level. There are links that tells you how, but basically, the side to side distance from the ground up of the blade tips should be within 1/8 inch. The front tip should be 1/8 to 1/4 lower than the back tip. Of course you want to remove the spark plug before turning the blades for safety. I repaired a John Deere that had the belt coming off and this fixed it.

Dont you just love people who ask and recieve advice on these sites but never come back on to tell what the outcome was so it can help others? So nice of them.

He may been that guy that made headlines about a year back. "Man shoots lawnmower"

This is an old line so I hope this info will help someone if not the original poster.

texmat and others:
It is almost impossible to twist the belt the wrong way over the mule pulleys as the v of the belt will be upside down in the v of the pulley. ItâÂÂs hard to do and easy to see. I donâÂÂt think that you and the dealer both would have made that mistake.

Poor alignment shouldnâÂÂt matter much. IâÂÂve been using my CC 2166 to mow and level a rough 2 acre site. I bought it used and it has lead a very rough life for about 7 years now and the only repairs I have had to do have been caused by my own over use and abuse. With that thought in mind I have never had a belt die of old age. I have burned or snapped them by jamming something like a 2â sapling right into the belt or like yesterday it was a 4â rock jammed between the blade and deck resulting in new blades and welding and straightening the deck (again). It is never in perfect alignment. I was able to save the belt by hitting the pto button as soon as I heard the squeal and smelled the smoke. If you are jamming and burning the belt you will always have smoke.

If this is like the deck on my 2166 then the belt tension lever that you have to release to change belts puts tension on both the pto belt and the mower belt at the same time. If the tension lever is bent badly in one direction both belts will be loose. If bent the other way both belts will be too tight. Either way can cause failure. Hope this helps someone. rev-dup

Check that the flat outside of the belt is not rubbing against itself as the belt comes around the rear idler and maybe hits the bottom of one of the other pulleys coming back around the front idler base. It sounds like you have a friction point where the belt comes in contact either with "itself" or rubbing on a "fixed" part on the deck and friction is wearing(burning} out the belt before it breaks. A sloppy idler that won't keep constant tension(bad tension spring or no tension spring at all) on the belt or a cocked idler pulley due to a bad bearing. Make sure your spindles are bolted tight to the deck base and are the same height. Run the deck with the new belt for 20 mins. hop off the deck and check idler tension to see if it is holding and not loosening. Look to see if there are any rub points showing up by manually turning the a blade and looking accross the deck to see if things look level. If you smell burning belt something is rubbing and you have a friction point which you should be able to find as you'll find some place that's rubbed shiny or you'll see a spot where the belt is rubbing against itself on its trip around the deck while the deck is on. Good luck.