It keeps eating drive belts! It looks like the pulleys are not parallel. Can you align them? It appears to be spring loaded

Something moved and parts are no longer lined up

not heard of any issue with this. Look for worn bearings in the pulley causing it to be out of alignment which will cause the belt to come off. also, check to see if there is any type of tensioner to keep proper tension on the belt. It usually consists of a spring loaded device so it has some "give" to it under loads, with adds flexability to it.

1) Look for obvious pulleys out of alignment. Most pulleys on a drive system are 'keyed' and have a set screw or bolt holding them into position.
2) Most traction belts turn with the engine, so it turns all the time. Look for an idler pulley with spring attached that may be out of alignment.
3) Inspect the 'V' groove of the driven pulley for any foreign debris.
4) Inspect the driven pulley for damaged caused by another pulley or object striking the edge of the 'V'.

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Keep in mind that the mower deck gets to be raised and lowered into the desired mowing height, with no change to drive pulley (at motor) height. This requires a belt long enough to allow the furthest reach (usually with deck dropped to lowest setting) and a spring loaded tensioner pulley, to take up the slack (and keep the belt tight) as the deck is raised. There may also be a belt guide or two incorporated to help keep the belt from jumping ship in the process. Sometimes these are just a heavy gauge steel wire loop that attaches near the pulley to keep the belt from jumping if it gets slack. Possibly you didn't thread the belt through or under it properly, or have missed the tensioner pulley.

It could also be the tensioner spring is broke or has fallen off or become too weak. Have someone move the deck up and down (with motor off, and belt installed) while you watch to see there is any obstruction in path. Also look for the belt becoming loose at a certain point. Some tensioners have the spring built in to the pulley and you can't really see them. They have to be pre-loaded, by rocking the pulley spindle assembly against the spring force while you slip the belt over it. Sometimes the belt looks fine and not loose in static (not moving) condition, but when the blades are spinning fast and the throttle is closed with no load (no thick grass being cut) the blades momentum will cause a belt sag that is supposed to be taken care of by the tensioner. It can get pretty grimy down there, also very dry, dusty and caked with cement like old clippings. Check the manual and find out where your tensioner is, then check it to make sure that it can move freely and it isn't locked tight by debris or rust. Also good to check if there has been an update to your mower. Sometimes these problems cause a manufacter to offer a better spring, or change pulley sizes to correct a common problem.

What you describe is an indication that the serpentine belt is under a load that it is not designed to operate under. Either the supercharger is suffering impellor interference at rpms or the bearings are not spinning freely or the boost at rpms is producing excessive load on the belt. Take it to a speed shop that handles super chargers and can do a dyno test to see exactly what is happening under rpm and see if you can get a better quality belt to do the job.

When pulleys are in alignment in both planes - check with a straight edge laid against the face of the pulley - the belt shouldn't come off.
By alignment in both planes it means the pulley grooves should be exactly inline with each other and the shafts the pulleys are mounted on should be perfectly parallel with each other - in addition the belt grooves should be in good condition and each pulley should be round and unbuckled.

In the old days it was necessary to adjust pulley alignment with shims and as many pulleys were pressed steel, a few were egg-shaped by small amounts and usually due to rough handling, some were like a buckled bicycle wheel.
It is many years since those checks had to be made as part of building an engine though whenever a belt-related problem is encountered it is time to dust off the old methods.

When the belt runs true it doesn't come off but there is another reason why a belt doesn't run true and that is belt chatter that is caused by a defective torsional vibration damper or crankshaft harmonic damper...

Check the alignment of the pulleys, If they are not perfectly aligned the belt will be thrown off at high speed. Also check that the axles are parallel to each other because if a pulley rides higher on one side the belt will ride towards the higher point and be thrown off the pulley.

Hi,


You find the timing marks on the picture below.





Removal
Remove auxiliary 1. drive belts.
2. Support engine.
Remove:
Engine mounting and bracket.
Timing belt upper cover [1].
3.
4. Turn crankshaft clockwise to TDC on No.1 cylinder. Ensure timing marks aligned [2] & [3].
Remove:
Crankshaft pulley bolt [4].
Crankshaft pulley [5]. Use tool No.09213-60017.
5.
6. Ensure timing marks aligned [2] & [3].
7. Slacken tensioner bolt [6]. Move tensioner away from belt and lightly tighten bolt.
Remove:
Timing belt lower cover [7].
Crankshaft sprocket guide washer [9].
Timing belt.
Tensioner pulley.

Installation
Installation
1. Check tensioner pulley for smooth operation.
2. Check free length of tensioner spring is 46,0 mm [8]. Replace spring if necessary.
3. Fit tensioner and spring. Ensure spring is connected correctly.
4. tighten bolt [6].
5. Ensure timing marks aligned [2] & [3].
6. Fit timing belt. Ensure belt is taut between sprockets.
Install:
Crankshaft sprocket guide washer [9].
Timing belt lower cover [7].
Crankshaft pulley [5].
7.
8. Slacken tensioner bolt 1/2 turn [6].
9. Turn crankshaft two turns clockwise to TDC on No.1 cylinder. Ensure timing marks aligned [2] & [3].
Turn crankshaft slowly 1 7/8 turns clockwise until crankshaft pulley timing mark [3] aligned with 45° BTDC mark [10] on
timing belt lower cover [7].
10.
11. Tighten tensioner bolt [6]. Tightening torque: 42 Nm.
12. Install components in reverse order of removal.
13. Tighten crankshaft pulley bolt [4]. Tightening torque: 108 Nm.
Manufacturer: Toyota

1) bad pulley
2) bad pulley bearings or spindle
3) out of alignment
Mower to new to be having this problem
My guess bad bearing.

1.Your engine has an internal timing chain, not a belt.
Therefore I'm going to assume that you mean the serpentine drive belt.
Common causes for belt to fail is either a mis-aligned or damaged pulley, improper belt tension, or bad tensioner spring (if equipped with spring loaded tensioner) You mentioned a loose pulley but didn't say which one! That's what I'd look at first! Also, make sure that all pulleys have no "wobble" indicating a bad pulley bearing Most common: water pump or idler pulley.