Brand new mower deck belt keeps jumping off

   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#31  
Could you reference those numbers on a diagram please so we know that we are looking at the same thing.

Sure Tom. See below.
 

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   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#32  
The idler pulley is usually tensioned with a spring and arm that when you tighten it the pulley actually moves to tighten the belt - is your idler pulley arm free? The belt tensioning pulley should move in an arc like 2-3" - if the swing arm is tight loosen the bolt with penetrating oil etc to get it to move back and forth.

Thanks Carl. The idler pulley tensior arm moves freely. Bolt good 'n tight...
 
   / Brand new mower deck belt keeps jumping off #33  
Wow. This thing is really kickin my butt. I've been wrestling the deck out from under and reconnecting the belt a couple times every mow. To your point earlier, there is no side to side play in any of the mower blade pulleys, nor in the idler arm pulley; all 4 are brand new and tight. The other 2 idler pulleys, if that's the correct term, one (#52 toward the right side of the deck as you look down at it and facing forward), has just ever the slightest bit of play - almost negligible. The other one, #39, that the tensioner arm pivots on/about, is snug.

Every time the belt jumps, it jumps off the DRIVE (#12 or #11) pulley.

For a couple of weeks, after putting on new spindles, blades, and deck belt, it was doing okay. But I could only mow at the 3rd lowest position. As luck has it, I prefer to have it in the 2nd lowest ...and every time I put it in there, it usually always jumps. Sometimes not, (maybe after running in the 3rd position a while), but, for the most part I can't use the 2nd lowest position any more.

Today is a disaster. Went about 50 ft in the 2nd position and it jumped. Got it back on and started in 3rd position, jumped immediately. Thought the tensioner arm had too much up and down play, so I took it apart and put about an 1/8" washer in there to snug it up, which it did, put it back together, belt jumped. Got another used belt that was in good shape, put it in, didn't get 2 feet and it jumped.

Help me. Please help me. :). Thank you.

11 or 12 pulley doesn't seem to fit with this diagram. Normally these will launch a belt at the flat idler on the tensioner. Hence a good place to put an extra guide.
 
   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#34  
Ah, ya got me there. #11 and/or #12 is the drive pulley under the clutch & engine. I can get that schematic but thought it was self explanatory.
 
   / Brand new mower deck belt keeps jumping off #35  
In the perfect world, yes it would be. Your interpretation is spot on. I'm sure you've thought more about pulleys over the last month than you've cared to.
On to your problem. It is easy to think of a drive belt being pulled though the array of spindles and idlers. I find it helpful to think of the drive pulley pushing the belt around the array. Belt angle could possibly come into play here as well as a damaged (think split or badly wowed) drive pulley. But more likely something is momentarily stopping the belt and it gets tossed. I don't think that you had mentioned that the belt runs hot, have you? 196103 or 587686701 belt?
 
   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#36  
Interesting visual to consider belt being Pushed around. I have not felt the belt to see if she痴 hot. It is the 6701.

If I have the deck high off the ground, there痴 no issue. Low to ground and it jumps. To me, that suggests something other than to ease with which the belt is being pushed around the pulleys 😎. Wouldn稚 you think? It seems related to angle from drive pulley to the idlers. (IMHO).
 
   / Brand new mower deck belt keeps jumping off #37  
Set your tire pressure and check your deck pitch. I would set the front of the blade 3/8" below the rear for starters. It is fairly easy for a deck this size to pull back the front support bracket thus increasing the pitch and affecting the angle. For years they were attached with a more rigid dual draft arm in the front.
 
   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#38  
Set your tire pressure and check your deck pitch. I would set the front of the blade 3/8" below the rear for starters. It is fairly easy for a deck this size to pull back the front support bracket thus increasing the pitch and affecting the angle. For years they were attached with a more rigid dual draft arm in the front.

Thanks Tom. I'll try that!
 
   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#39  
Set your tire pressure and check your deck pitch. I would set the front of the blade 3/8" below the rear for starters. It is fairly easy for a deck this size to pull back the front support bracket thus increasing the pitch and affecting the angle. For years they were attached with a more rigid dual draft arm in the front.

Tom/All: All tires set to same PSI. About to measure height of mower blades (both front to back and side to side) and I notice the deck is MUCH higher on the right side, where the grass exits, vs. the left. The Rear Lift Link arms (that essentially control the height of the rear of the deck) are visually set about the same; the same amount of thread exposed. I do notice that I can push the mower deck from right to left, which then obviously changes the height of either side.

How do I know if my deck is centered? That little Anti Sway Bar doesn't seem like a great control mechanism. I could put a few washers in on the end of the anti sway bar to keep it back to the left a bit but that seems hokey. When I look at the front, underneath, and line up the Front Lift Link Assembly to the front of the deck (the frame of the front/center deck wheel), they appear true/in-line. When I measure the tops of the two outer spindle grease fittings, they're almost the same... Just not sure how to ensure that the deck is centered.

I'm going to adjust the Rear Lift Link arm on the left so that the deck 'hangs' at the same height on both sides. But I think this may be the root of my problem. Again, the outer right edge of the deck (as you sit on it) is about 1.5" to 2.0" higher than the left. Once I get it level, then I'll confirm that the front of the mower blade(s) is between an 1/8th and 1/2" lower than the back.

Thoughts? Thank you.
 
   / Brand new mower deck belt keeps jumping off
  • Thread Starter
#40  
Annnnnnnnnnnnnnnnd I want to punch myself. Over and over... Spent about an hour confirming everything was set properly, and I got about 30 feet of mowing on the 3rd lowest setting, and it was too high. Put it on 2nd lowest, went 10 feet, jumped.

This time, for whatever reason, not off the drive pulley but off the idler pulley with the belt retaining bar/arm.

At whits end.
 
 
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