Replacing MTD Yard Bug drive belt

javertMay 29, 2007

First: I hate to admit that I own one of these things. But, my wife wanted it, and she REALLY looks cute, in her short shorts, on it.

Second: The owners manual is darn little help. In a nutshell, it says "remove the old belt, and install a new one." (Okay, it says more than that, but doesn't really tell you how to do the job.)

Third: My repairman didn't want to work on it - he hinted that he would replace the belt for about a thousand dollars.

Fourth: You will need an impact wrench to remove the pulley from the engine. This is a good excuse to buy an air compressor and assorted tools for it. (Although the book says to use a 9/16" socket, you would have to grind the head of the bolt down from 5/8" to 9/16" for that to work; it's easier to use a 5/8" socket.)

Fifth: If you have determined that keeping the machine running is worthwhile, here's how to do it:

1. Lower the mowing deck all the way

2. Remove the belt guard from the top of the mower deck

3. Disengage the mower drive belt

4. Turn the machine on its side (the right-hand side)

5. Use an impact wrench with a 5/8" socket and remove the bolt from the dual pulley on the bottom engine shaft

6. Grasp the rear of the mower deck and swing it down and toward the front to get it out of the way so that you can remove the pulley

7. Pull the pulley assembly down

8. Find the square key that falls out on the ground - the one that locks the pulley to the shaft

9. Slide the new belt over the top of the axle, and place it on the upper of the two pulleys (the mower deck belt goes on the lower pulley).

10. Slide the pulley assembly onto the engine shaft

11. Align the pulley slot with the slot on the engine shaft, and install the square key (found in step 8)

12. Install the washer, lock washer, and bolt that you removed in step 5.

Now turn your attention to the variable-speed pulley assembly - the two-pulley assembly that is up against the back of the frame. It's held in place by a bolt that goes through the frame. You will note that intelligent engineering placed the pulley too close to the frame to be able to slide the belt around it, so you have to remove the pulley to get the belt on. The belt that you have just replaced goes onto the TOP pulley of the two. Now replace the pulley assembly and tighten it up. Route the new belt around the idler pulley, and you're done. Except, of course, for turning the mower upright (particularly important) and re-installing the deck belt and belt guard.

Now, to confuse the issue: The Yard Bug uses two (yes 2) identical belts to provide propulsion (MTD PN 754-0453, available off eBay from $25-40 each, or from Agri-Supply for $10 (A-S #63379).

Your owner's manual refers to the belt that I just told you how to change as the Upper Variable Speed Belt, although it is the drive belt nearest the bottom of the machine. It is on the upper part of the pulley that is attached to the engine shaft, and goes around the upper variable-speed pulley that is at the back of the machine. The other drive belt (Lower Variable Speed Belt, according to MTD) is above the transmission (just under the seat), and goes around the lower of the two pulley on the variable-speed pulley (back of the machine). So, the upper drive belt is closest to the ground, and the lower drive belt is farthest from the ground.

BUT, in MTD's defense, the upper drive belt DOES go around the upper pulley of the assembly that mounts to the engine shaft AND the upper pulley of the variable speed pulley (the one at the back of the machine). The lower drive belt, which is the top-most belt when the machine is upright, goes around the transmission pulley and the lower pulley of the variable speed pulley. GOT THAT?

If it's any constipation ... er, consolation ... the lower drive belt (the top-most one) can be installed by removing only the variable speed pulley at the back of the machine.

Now that I've figured all that out, and have new belts on that piece of (whatever), my only problem is that the engine won't start. I've got a headache. I have a strong urge to say nasty things about MTD engineering ... and quality. But I can overcome ... and so can you.

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True Story:
5 years ago my dad calls me up and asks me to bring my trailer over, and pick up his new tractor. He owned 5 acres, mows about 1 acre, and has money. . I'm thinking I will be picking up a Gravely or something similiar, but when I pick him up, he directs me to Lowes, and we pick up his new Yard Bug!!

My nephew, who is a worthless idiot, says he cannot figure out the controls on the Bug, so within the year, my 80+ year old dad is mowing the grass again.

My brother Patrick stops by dads 4 years ago, sees the grass needs mowing, and discovers the Yard Bug. He promptly wheels it out, sees the custom tubing my dad has modified to feed ether directly to the carb, among a few other mods, starts mowing, has an absolute FIT fearing the Bug is going to roll over, disappears for an hour, returns with a Simplicity Regent, Brand New, which he gives dad with the advice he must "scrap the Bug". (unsafe at any speed)

Dad continues to use the Bug, the Simplicity is too nice, he says, so 2 years later we hijack the Bug, and sell it at my house, thus forcing dad to use the Regent.

Dad loves the Simplicity, and takes it to his new house. Bug is gone, living somewhere in Ohio, never to be forgotten, and hopefully, never to be seen again.

    Bookmark   May 29, 2007 at 10:41PM
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I had an MTD Yard Bug. I bought it with the house. 2 mowing seasons later, I now own an old Deere LX176.

This thing was just ridiculously slow. It couldn't really pull an aerator, though I did. The deck's shape was hardly ideal for mulching, and the blade had really poor lift (despite being a mulching blade.)

I too had to swap out the drive belts. It wasn't too bad a job- took me about an hour or so to do, using only the instructions in the owners manual.

I did end up getting $250 for it when I sold it, which was nice. It was just not a good machine- for what these cost new (about $1000), you could get the lowest of the low end tractor or a good used one, and it would be a better deal.

    Bookmark   May 29, 2007 at 11:07PM
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Let's see the wife, in the shorts, first.

    Bookmark   May 30, 2007 at 8:13PM
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MTD = J.U.N.K.

    Bookmark   May 31, 2007 at 6:56AM
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Ah, Fish, I wondered what it would take to get you out of the woodwork. I suspected that the short-shorts reference might work! Glad to see you're still hanging out in these parts.

    Bookmark   May 31, 2007 at 1:49PM
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I just bought a used one with the 9 hp engine. Yardman yardbug. Belts are off of it so have to reassemble it. Charged the battery and it cranks so engine free. You guys make me think I could have spent my $150 better elsewhere. But I wanted something I could get cheap, repair and get running to mow our lawn. The bug can't possibly be that bad if it is all adjusted just right...maybe, huh?

    Bookmark   October 20, 2008 at 2:14AM
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All things considered, my little yard bug has been a champ. It has been mowing an acre, including big hills for the past 12 years. The batteries seem to go fast (proably because one has to empty the hopper so often) but otherwise it has been a real work horse. If anyone knows how to replace the cable that connects the pedal to the mower deck I'd be grateful. Trying to mow just ahead of snow flurries yesterday I discovered it had snapped.

    Bookmark   October 29, 2008 at 3:10PM
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Thank you for the information about purchasing a belt...NOW FOR MY COMMENT OF THE YARDBUG. I argue the following. Let me give a 6th grade class the project of designing the belt configuration and I guarantee that they will outdo...the "expert engineers." It is a joke when we think the "experts" have carefully thought out the design of this and many other rider mowers. The task of loosening the main engine shaft to replace a nothing less than a joke. The one thing I'd do if I ever purchase a mower again is check the ease of replacing belts. I don't like engineering "jokes."

    Bookmark   May 13, 2009 at 3:02PM
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Well hereit is easter Sunday 2010 and my Yardman Yardbug still sits beside the back door...Don't know what happened 2009 but right now I left the battery in all battery...Schucks Auto I think has new batt's for $19 so will probly have to get one. Think my last battery probably froze solid. Got the engine running last time I worked on it but runs full speed and can't get it to drop to idle speed and still have all the belts to reinstall. Hope we have a warm spring and not so warm summer so i can actually get this bug together and happily mow some grass.

    Bookmark   April 5, 2010 at 12:38AM
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How do you stop the engine from turning when removeing drive pullies and to reinstall. Thanks Ron

    Bookmark   May 15, 2011 at 5:07PM
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That is where you use an electric or pneumatic impact wrench.
You can remove the flywheel cover and have a helper hold the flywheel nut with a socket and breaker bar while you work the lower end of the crankshaft/pulley.
Impact wrenches work best and easiest.

    Bookmark   May 15, 2011 at 8:58PM
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Ron, if you can buy, beg, borrow, or steal an impact wrench, you don't have to keep the engine from turning. A pneumatic impact wrench will just "walk" it loose without turning the engine.

Mownie gave you the way to do it with hand wrenches, but an air compressor and a few tools for it are so useful that, IMO, every handyman homeowner should have one. You can get a small compressor, impact wrench, and impact socket set for less than a hundred bucks (if you don't need high quality.) And, by the way, you can actually run an impact wrench, or many other small pneumatic tools, BRIEFLY with a 5-gallon air tank, by filling the air tank from a friend's compressor.

Glad to see that my original post on the forum is still being referred to.

    Bookmark   May 15, 2011 at 10:04PM
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Replaced the freaking belt and now the damn thing won't turn over. I spent closed to 3 hours doing it.

    Bookmark   September 24, 2011 at 9:41AM
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"Replaced the freaking belt and now the damn thing won't turn over. I spent closed to 3 hours doing it."

If you tipped the mower on its side and motor oil from the crank case got into the Cylinder you could have "Hydro lock". That means oil is in the cylinder and the engine cannot crank (oil can not be compressed).
You must pull the spark plug rotate the motor to get the oil to push out of the spark plug hole and then clean the spark plug and reinstall it. The motor should run ok if it was Hydro Locked.
Hope this helps!
Tony C

    Bookmark   July 14, 2012 at 9:56PM
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Those who wrote this damn manual should be given a sentence.
These Idiots don't tell you that there are 3 belts on a 247.27022 Craftsman Yard Bug, one for the deck & 2 identical part # 954-0453 for the drive & engine. I called sears & they didn't even know. Thanks to member Javert that made me aware. I just hope I will be able to tackle this job changing these belts by my lonesome. Little 70 y o lady with lots of MOXIE!!!

    Bookmark   August 8, 2013 at 8:47PM
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Well, I set off to replace my belts in this way. Undoing the engine bolt worked eventually, though I had to heat it up with a gas gun then hit the end with an impact wrench. Unfortunately that's where things fouled up.
The pulleys were seized on. I tried a seriously strong puller, which only bent the pulleys out of shape. So - lateral thinking........ The things that are stopping the belts coming off are the keeps - two rods down the sides of the pulleys. It turns out that they are only held on by half-inch gripper nuts at the top, and are easily removed. Now the belts are free to drop off the pulleys.
Further round the system there's a silver coloured link thing. Undo the bolt at the link end, then undo the nut holding the pulley. Shift the pulley out along its shaft so that the belt can clear the keep. There's a big spring in the way, but you can manoeuvre the the belt round it.

That gets both front belts off and back on. I haven't tried to get the short belt at the back off, because it looks like you have to take the rear axle off.


    Bookmark   March 15, 2014 at 9:55AM
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