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Model 917.203900....2014 with Briggs 22 hp with RS 800 transmission

my mower has 4 drive pulleys and I am having an issue with the drive belt coming off. The pulley its coming off from is the smaller back one near the transmission. It has a belt keeper on it and I have it bent down as far as I can. I never comes off while moving, only after I stop and back up to cut grass near curb or flower beds.

It takes 30 seconds to put back on, but would prefer it to just stay on like it should..any suggestions as to what could be causing this?

Thanks

Make sure the transmission support brackets are still attached. If the bracket is not connected will allow the transmission to pivot when starting and stopping. Also will cause cracking at the connection points at the frame/axle area

Thank you. Where would they be located?

Either on the front of the transmission or the front corners. different mowers and transmissions use different setups so need to look around the front and see if everything is attached.

Some will have both front coners, some just one. Some will have a connection on the front and others will be the front top.

The RS800 anti-rotation bracket are on the front corners bolted to the frame with L brackets. On the transaxle the bolts a thru with the brackets on the top side of the mounting holes.

I checked everything I could get my hands on and it all seems tight. I will keep looking and see what I can find.
Thanks for all the tips.

So the motion dirve belt comes off:

Here is a link to download a owners manual.
If the link don't work do a on-line search and then download from sears parts direct. I did not look for a parts diagram. The belt routing diaqgram is on the bottom of the floor pan on yours.

Look at page 55.

The belt being stretched or wrong belt being to long or too wide will cause such plus if the idler pulleys are worn out.
Some of that version tractor have two rear pulley, some only one so don't get confused if it shows two rear ones and you only have one.

Thanks Forest,

I have the owners manual and the belt routing sticker under the tractor. The belt I ordered came from Sears Parts direct as well as the new pulleys. Mine does have the two rear pulleys which are about 3 months old.

Was the old belt also jumping off or did the problem surface AFTER you replaced the belt and pulleys?

My bad.... I got this drive belt from Lowes. I think the belt I took off was possibly the original, but the belt stayed on the few times I mowed with it before replacing.

If you still have the old belt take a string or tape measure and measure the belt OD and compare it too the new belt and also compare the width.
Your new belt is probably little too long. A hint that it's slightly too long or wrong is the shuttle clutch has to be push down further to get a go.

I use a upholstery cloth tape measure from wal mart at about $4 and now days I ALWAYS measure the length of a new belt BEFORE INSTALLING BECAUSE like you I just throwed them on because they are SUPPOSE TO BE the right size. Not fun labor and cost wise when a new belt is installed and it's then used and the wrong size. I see several belts on ebay with same MTD part number and they are LISTED AS different sizes in length and/or width. The sellers don't even know why when asked about such. Randys small engine parts on ebay is one example of several same part numbers and different sizes and when asked they don't reply nicely.

I've found some new belt to not be as labeled and I always measure the old belt that being removed. Sometimes the old belt was on purpose re-sized due to issues such as yours by a previous guy working on the machine.
Usually they are little bit too long if the pulley are correct size and Ok.
If you install a too short belt on your shuttle clutch tractor you won't have a Neutral. Also the the clutching swivel double pulley spring has to be strong and connected to the proper place for good tension.

Belt specs depends on where you look. Sears has it at 1/2 x 101-1/6 Stens has it at 1/2 x 100.25. I can go out to shop in the morning measure the OEM 592855001 belt as I got two them on the shelf.

StarTech said:

Belt specs depends on where you look. Sears has it at 1/2 x 101-1/6 Stens has it at 1/2 x 100.25. I can go out to shop in the morning measure the OEM 592855001 belt as I got two them on the shelf.

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Thanks Star. I just ordered that belt today from Sears

So I wanted to update this one again..the drive belt was purchased on Amazon, not Lowes.

I kept having issues with it coming off, usually after stopping and shifting to reverse and then back forward. I ordered the belt from Sears parts and installed this weekend. It was maybe 1/4 inch shorter than the one from Amazon. The one thing I did find was one of the idler pulley nuts was almost at the bottom of the bolt that holds it on. I had to grip it with vice grips and use a thin wrench to tighten it back up at least a 1/2 inch.

So I have cut grass with it twice now and the belt has stayed on...hoping this solved my problem!

Also, You really have to keep a heads up on idler pulley alignment on that type motion drive. Sometimes just removing a idler to check the bearing or to replace a un-noticed spacer on top of the idler will fall off and not be noticed for re-installing/re-assembly.

Good point Forest

thinking my father in law tried to remove it at some point and didnt finish. It does have the carriage bolt head up above that is hard to access.

thinking my father in law tried to remove it at some point and didnt finish. It does have the carriage bolt head up above that is hard to access.

Your other belt will probably work ok now that you fixed the idler.

Forest#2 said:

thinking my father in law tried to remove it at some point and didnt finish. It does have the carriage bolt head up above that is hard to access.

Your other belt will probably work ok now that you fixed the idler.

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It probably would..got it put up for a spare