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Mower deck belt got smaller

Geo-TH,In

Geo-TH,In

Well-known Member
I have cheap 38 inch mowers for tenants to use. I worked on 3 of them today. One I had to replace the mower deck belt. It was so small the blades turned when I tried to start it. I had a spare belt. Replaced it with a belt with the same #. I only use Kevlar belts. The old belt had no signs of wear, just got smaller on me. Have you ever heard of such a thing?

The other had a single cylinder 15 hp briggs. I had to adjust the valves to get it to crank. It acted as if the engine was locked. After adjust the valves, it worked as it should.

Last year I had to replace the cam on a friends 18 single cylinder briggs. The decompression part of the cam broke. I'm glad I didn't have cam issues.
 
On the shorter belt my guess is that deck tightens the belt by a spring that pulls the deck backwards. when you raise the deck that is what moves it forward to release the tension on the belt. Something is wrong that it isn't getting pulled forward, could be bent brackets or??
David
 
Yes, but not on a mower. Our Massey super 92 combine never sat out. During harvest if it wasn't going to rain it was allowable. I can remember a couple of times a pop up shower happened in the night. All of the threshing was driven with a flat belt (like on a tractor flat belt pulley). When it had gotten wet and dried it shrank. You would have to start the combine with everything spinning. Then if you could get the lever engaged for a bit it would stretch out to normal.

Must have been OHV engines? On flat heads you loose compression with valve/train wear. With OHV you get more - valves open late and close early.
 
someone replaced the belt with the next smaller size. Seen it happen several times.
 
I do all the work on mower. The smaller belt once worked. It has the same number on it as the belt as the bigger belt I just put on. Some how the belt got smaller with use, no signs of abuse.
 
Probably got damp and shrunk. On the old grain binders etc, canvas was always loosened at the end of the day as they would shrink and could tear.
 
I will recommend that you work on loosen up the belt tension er. After years of not being moved they will stick in their favorite spot.
 

100% with SDE, idlers stick in the darnedest places. The last 3 times my belts shrunk, it was due to the idler locking in.
 
That must be a MTD.

1. How rusty are the pulleys? If rusty at all they are going to drag and the blades won't stop.

2. Gotta have the belt covers around the spindles and the belt guides around the engine pulley. Otherwise, you are wasting time. They keep the belt pinched up close to the pulleys so they don't drag when the belt is slacked.

3. There is an adjustment on the link that works off the lift handle that controls how much the deck pulls forward. The one time I had one that would not cut off at all, the weld was breaking on the arm that pulled the deck forward.
 
I know you said it shrunk, but did you actually measure it, or just the fact that the new one was ok, but the old one would not disengage. I have seen V belts that sat a while actually get fatter from absorbing moisture, especially if over a long damp winter. When they got fatter, they rode higher in the pulley grooves and was the same as if they had gotten shorter. I have a Mott flail on a Farmall cub that you loosen 3 bolts, pull a lever, to adjust the belt and tighten the bolts, so their is no spring in it to compensate for wear, etc. The first use in the spring it is so tight you can pluck it like a guitar string, and I loosen it to prevent damage to the bearings. After it is used an hour or two I have to tighten it again to prevent slipping, and it is ok then all summer.
 
It got smaller. It worked when new. The replacement belt has the same #'s and it's
longer by over an inch. No need to measure. Old one didn't work. too tight, new one
does. It simply got smaller and no signs of wear like glazing or cracking.
 
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