Mower slowed down, now won't go.

sixfootrabbit

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I have a Troybilt 13YX79KT011, which slowed to a crawl, and now won't go. Only paid $50, so at least I got a great engine. Anyway, the drive belt is stretched beyond belief and I cannot get it anywhere near proper tension. Then I noticed that the transmission bypass lever is very easy to move either way, and will not engage the drive when pushed in. It is the same both positions. For sure, however, the belt is too stretched, but I have a feeling the bypass lever problem seem to be a likelier culprit...any thoughts? Thank you, all.
 

Scrubcadet10

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belts generally won't stretch, but the V wears into the pulleys making the inner diameter bigger making the belt looser, I would start by replacing the belt first so that you can ensure the trans is function properly.
MTD shows the belt PN 954-04252
 

bertsmobile1

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Sit down for 10 minutes cross legged on a rug and go Ohmmmm.
Clear your mind of all the it is "For Sure Of " because it is wrong.
Now with your fresh eyes devoid of pre-concieved opinions go to parts Tree, Jacks Small engines or some whee similar and print out a copy of the transmission / drive parts break down
Raise the mower and check that all of the pulleys and springs are actually there .
Look at the shape of the belt in the diagram and compare it to the shape yours is .

A belt that is 2" too long will still drive
A kevlar belt will not stretch more than 1/4" before it snaps .
The bypass lever is just a tap.
Like the button on your dunny all it does is open or cover up a hole for oil to pass through so there should not be much resistance to it moving .

Lots of people have inferiourority complexes so will happily sell a $ 500 mower for $ 50 rather than admit they made a mistake putting a belt on .
 

sixfootrabbit

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From what I could see from underneath, the "loose" belt is running the correct path, and springs are attached. Actually my real concern is the loose feeling bypass lever. The lever is attached to the bellcrank, but it is as loose pushing as it is pulling. Would it not be plausible for the mechanism inside the transmission to have failed in the disengaged position with the pull handle being so seemingly non-functioning. Either position, it will not lock the wheels.
 

bertsmobile1

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To test the bypass valve you simply push the mower on the ground
Valve open the mower will push easy
Valve closed the mower will not push easily
The valve is nothing more than a rod with a hole in it so there is noting to make it stiff, click , klack offer any resistance , feel like a gear shifting .
It is just a HOLE .

If the correct belt is fitted properly turning the belt will turn the engine over compression ( spark plug lead removed for safety sake )
If not then at lest one ( or more ) of the following has happened:-
engine / tranny pulley worn out & belt is running on the root of the V
Belt is too long
Brake pedal is not fully returning
Spring missing in the wrong place or cut through the anchor point
Belt routed wrong through the clutch idler pulleys , very common on this model because they are both flat pulleys not a flat & a V .
Tranny pulley stripped so it is not turning the input shaft

Not connected to the belt
More than one "no drive" repair has been to replace the drive key in one or both rear wheels which fell out when the owners was fixing a flat tyre.
 
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