My belt falls off!

I swapped my rear pulley from a 9 to a 6 inch. I got the belt size I needed and put it on. Now when I start it the belt comes over the top of the rear pulley and gets pulled ahead off of the front pulley. I thought maybe it had something to do with the pull start I rigged up to it. To check I tried starting off the electric starter too, same problem. The belt seems to have the same amount of tension as the original belt and pulley setup did. Also all belt keepers and guards/guides are in place and correct/untouched. What is the problem!?? Do I needed to make a tension pulley to pull the belt closer to the frame and take some slack out of it or is the problem something else? Also I can pull the belt tight only a little bit before the clutch starts to pull into it's depressed/slacking position. Any ideas?

Are your pulleys lined up exactly?

Belts are one of the biggest pains in the butt when modding. The most common point the belt would fall of for us was when you would be going at high RPM and hit the clutch suddenly. The belt just opens up and drops off.

I strongly recommend upgrading the belt retainers/guides. We built belt gates - pieces of rod stock welded across the bottom just above and just below the belt. We put them in as close as we could get to the pulleys and still be able to slip the belt through to remove or change it.



Edited to add: Chopper is right to check the pulleys are lined up and in the same plane before other mods.

Plus, help brace the frame more. Very nice idea there. Mine falls off too, so I might use that idea.

I gave another inspection and found out that the rear pulley sat lower than the stock one so I made a spacer for it and it works fine now. I just need to build a tenisioner for it because it slips a little in higher gears when on uneven terrain and going uphill

A made an adjustable belt tensioner using the two idler pulleys from the mower deck. one can be adjusted closer or farther away from the other. Both are mounted on a spring loaded bracket. All of the brackets came from the deck.

That looks like it works great. What I love about my Murray is the simplicity of it. It has three belts, engine, clutch, and transaxle. After some tinkering I decided that I could build a tensioner for it very easily. All I have to do is drill a hole in the top of my frame so that it lines up with one of the holes on the bottom. Then I can put a bolt in there with a sleeve on it so I can run the belt inside of it and have something of a roller to decrease friction. Then once I adjust my clutch it will be all hunky-dory. That will also stop the belt from rubbing on the steering column shaft.

my craftsmans belts stay on actually rather well, despite the fact i have removed ALL tabs / retainers. hmmm???