MTD Deck Vibration

[lefty]

Model 13RN772G029
Serial: 1B118B10093

I did new belts and after noticed a kind of rhythmic, intermittent vibration when the blades are engaged. Don't know if it was there before because the owner mows with headphones. I did mention it to him and had him test it out and he then noticed it. The point being, I don't know if it was there before or not but I guess that's kind of irrelevant at this point.

I observed the idler arm vibrating, bouncing up and down a bit in 2-3 second intervals. The blades are new, spindles in good condition, pulleys aren't wonderful but there's no play in them. But I can move the idler arm up and down quite a bit. It seems that the shoulder spacer, number 37 on the diagram, is bottoming out before the arm can seat flat on the mount attached to the deck. This is resulting in some play there.

My question: Should this arm have a little play and could this just be a bad pulley causing drag and thus the vibration? Or should these parts seat up nice and tight? Meaning the arm to the mount that it pivots on.

On a side but related note, I'm not seeing a part on the deck diagram. It's a spacer about 1.5 inches long that goes between the top part of the mount and the deck. The bolt for the pulley slides through it and then a nut connects under the deck. It's located where number 48 is on the diagram, which they show as a bolt.

Model parts diagram:
https://www.mtdparts.com/en_US/prior-year-models/yard-machines-riding-lawn-mower-model-13rn772g029/13RN772G029.html?d=t#/MTD_Merged_Data_Staging/13RN772G029_(2008)/Deck_42_Inch/509cb6bf-ebc9-4c39-95ef-4911fefd7afb/78547bc6-ee80-4af4-a02c-fd660ee812ea/y

Thank you. I should add that this machine takes a beating. As stated, the owner cannot hear what's going on when mowing but being that I live across the street...I hear it all...the rocks, branches, and even the occasional curb. It's horrifying.

[lefty]

Disregard the bit about the spacer...I found it. It is number 48.

[Arkie]

Idler pulley jumping is a clue.

But:
IMHO:
if I knew that the operator is that rough on his own eq I would kindly tell him in a nice way since he is your neighbor that I just do not know what might be the cause of your mower issues.
I would send him to the most expensive place I could think of for a diagnosis.
(as a wake up call for him)

I've got a neighbor that is the same way, he mows over large rocks and does not even bother to take time out and remove the rocks. Lets his grass sometimes get waste high and tries to mow with a low cut and runs over large flint rocks that Ronnie Milsap can see. He knows I work on stuff and sees me repairing lawn tractors and has ask me to check his eq and I kindly decline, just too busy right now.

[KE4AVB]

I haven't seen this particular deck design yet. But part 37 and 2 do wear quite a bit on other MTD decks. Also check that the spindle pulleys are running true. I have seen bent and wobbling. Plus check the idlers for bearing operation as a rough spot can cause problems too.

[38racing]

I have a guy's mtd here and one spindle pulley had a wobble. Not sure what you have to do to get that. He said he had burned the belt. I have another lady's here that had the blade end bent down 90 degrees and loose blade. Spindle shaft star gone on bottom and top pulley star was gone too. With that replaced and new blades I see the other side that blade is not even distance. Blade on that side also had a bent end. Bent deck or spindle issue?

[SUKI]

I have straighten a lot MTD decks from impact damage. Sometime BFH and a heavy metal rod gets a work out along with myself. Strange that I don't see many bent spindles but already had five this year.

[38racing]

I'm guessing that a good solid hit that bends a blade end down could bend the short exposed threaded end of the shaft? I've got it all back together so don't plan on swapping blades to check it out.

[SUKI]

Actually the bends have been higher up pass the flat star disc; just before the bearing. Even though this a 3/4 od shaft it still can be bent. I can usually see it by spinning the shaft with the blade off using the spindle housing as a reference point.

[KE4AVB]

I have the same with AYP/Husqvarna spindle shafts lately. Are they using cheaper steel? For years customers came with bent blades without any shaft damage; of course, I got a few broken spindle housings.

[38racing]

I had to use both the new and old blade washer because the aftermarket spindle shaft didn't have enough thread in it for the bolt to tighten.