Bad vibration....Troy Bilt Rider

[RMR]

Hoping to find a solution here. I'm working on a 2011 Troy Bilt Pony model 13WN77KS011. The issue I just can't figure out is a bad vibration when the blades are engaged. The engine runs good and very smooth when not spinning the blades. This is a mower I bought not running for a flip. I have completely rebuilt the deck with all new components (some I replaced while chasing this issue), as well as a new belt and blades. As soon as you engage the blades, the entire mower shakes. I first assumed an imbalance in the blades, so I took them off and it didn't change. While it's not as bad, it's still there. I have gotten down low to observe the deck drive assembly while running and can see the shaking in several areas. Thinking it was the idler arm, I took it off and recentered the worn, ovaled pivot hole by welding it back in and redrilling it, with the same results. Someone suggested a bent crankshaft, but I think I would see visual signs of it in the crankshaft pulley while spinning, and I don't. My next step was going to be swap belts, but I've got my doubts. Anyone run into this on a rider of any breed? I have attached a link to a video of the deck components running at a low rpm. It gets worse as the rpms increase.

[bgsengine]

Hoping to find a solution here. I'm working on a 2011 Troy Bilt Pony model 13WN77KS011. The issue I just can't figure out is a bad vibration when the blades are engaged. The engine runs good and very smooth when not spinning the blades. This is a mower I bought not running for a flip. I have completely rebuilt the deck with all new components (some I replaced while chasing this issue), as well as a new belt and blades. As soon as you engage the blades, the entire mower shakes. I first assumed an imbalance in the blades, so I took them off and it didn't change. While it's not as bad, it's still there. I have gotten down low to observe the deck drive assembly while running and can see the shaking in several areas. Thinking it was the idler arm, I took it off and recentered the worn, ovaled pivot hole by welding it back in and redrilling it, with the same results. Someone suggested a bent crankshaft, but I think I would see visual signs of it in the crankshaft pulley while spinning, and I don't. My next step was going to be swap belts, but I've got my doubts. Anyone run into this on a rider of any breed? I have attached a link to a video of the deck components running at a low rpm. It gets worse as the rpms increase.

Harmonics and probably a weak idler arm engagement spring plus worn out draft arm shoulder bolts or J-pins - lots of little things going on add up to the harmonics involved causing the idler (the one closest to you in video) to bounce a bit Very very common on MTD machines and I have seen them far worse than that.. It's an MTD , not a Mercedes. - The vibration is going to get worse as the unit is used more and the attaching and pivot points wear further. Also make sure it is a OEM belt - only needs a slight imperfection in the belt to give it that "idler bounce"

[RMR]

I hear what your saying on the harmonics. But this one is REALLY bad. I'd never consider this as a "normal" vibration for a mower of any age much less one that's only 6 years old. I mean, this thing makes the engine flex the frame at the mounting plate. I'll try the belt swap and see what happens with that. But as it is, I'd not feel right selling this one in it's current state and put my name behind it. I'll probably have to hang on to it and wait for another TB to come through the shop and swap decks around to see which one the problem follows....

[bgsengine]

Since there's nothing really visually obvious (other than belt hop) in your videop and you're saying it is so bad its flexing the frame at the engine - Have you pulled out the engine bolts and check the bolt holes for "egging" ? - these (as well as cub cadet, and any other MTD brand) are notorious for the engine bolts working loose (We also see this a lot on the Husqvarna Outdoor models - formerly AYP - as well) - bolts might feel tight but if the holes are dug out from bolts having been loose at some point the engine could actually be shifting around. But from what I can see in your video, pulleys appear to be all in good shape and running true - only thing noticeable would be that one idler "bounce" - belt problem, a bit of debris in a pulley v-groove, loose engine bolts, poor quality belt, weak springs, worn out deck hangers (j-pins and draft arms as noted) a lot of things can cause that belt hop on your idler arm and that's probably being "magnified" through harmonics making a little "shake" into a major vibration.. Does the vibration change or vary as you vary the engine speeds? or does it simply increase frequency as engine is sped up? (and what's the engine running at RPM-wise?)

[KE4AVB]

I have had few MTDs where owners tried install an auto parts house belts on them. A standard inch won't work.

Make sure the belt length is correct. This mower uses 1/2 x 96-1/2" belt but by putting a 96" belt it will shake you to pieces. Even my little Bolens will do it if you drop 77-1/2" to 77". Simply overloads the engine. Only seen one that would and needed the standard size but that was due to highly abused deck that had welded several times.

[38racing]

I just dealt with a vibrating noma 43" deck. Idler bolt (NLA) was worn and arm holes worn ($100 with brake pad , maybe $50 without). I redrilled arm and used a bushing and wheel bolt. Still vibrated. Belt I thought was new and ok. I happened to have a 39" that would fit (with its own belt) and it ran fine. So I decided to swap spindles even though there was no play in them but I was concerned about one of them. I was in the middle of the spindle swap from 39" to 43" when a friend came by. I explained and he noses about and shows me the belt. A six to eight inch section with the inner V point way worn narrow. Now I did continue the spindle swap and got a new belt. Runs ok now. Interesting on belts is that both are aftermarket but sporting the NOMA OEM number. Both by Oregon with same Oregon number. Bad one was black and had flat outer surface, made in USA. New one is brown with slight curve on outer surface and made in Mexico.

[creia]

"This is a mower I bought non-running for a flip."
Want to end up with a MILLION dollars buying, fixing up, and selling mowers?
... then start with TWO million!!
Sorry, I could not resist.
Michael

[KE4AVB]

"This is a mower I bought non-running for a flip."
Want to end up with a MILLION dollars buying, fixing up, and selling mowers?
... then start with TWO million!!
Sorry, I could not resist.
Michael

Very reason I don't buy other people problems. Usually if they want to sell it, it has a lot problems along a lot make shift repairs. Here I just repair them. I got pay my bills and some left over in case I want eat out. Grazing with the Cows just don't get it.

But seriously lets see I can figure this one out as it will help all of us later. Meanwhile fixing my mower, Went to cut grass and gas was leaking out of the carburetor. Fuel line at carburetor is nothing but mush. Oh well even us techs got to fix our own problems sometimes.

[38racing]

i notice that it doesn't have the springed J rod connecting deck to lift arm. did mtd vary that on the 700 series?

[bgsengine]

i notice that it doesn't have the springed J rod connecting deck to lift arm. did mtd vary that on the 700 series?

Yeah - depends on deck size option smaller decks were kinda perma-fastened (not easy to drop) with lots of hairpins and rods to unhook.