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Allis Chalmers 611 LTD keeps breaking deck belts

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I've got a 1985 Allis 611 LTD with 36" mower deck that keeps breaking deck belts. All the pulleys line up and everything spins free. I'm getting about 2-3 hours out of a belt before they break. If anybody has any ideas that'd be great. This is getting expensive.

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GrincheyOne

Nick,

We are talking about the classic 1690838 36" deck, 2 spindles, 1 idler, 1 drive pulley. I agree if You are speaking of OEM belts #108505 ($28 a pop).

I ask,

Are the belt-stops (5) adjusted per the ops manual?

Are the spindle brakes adjusted per the ops manual?

Is the PTO tension adjusted to specs?

What is the condition of the PTO pulley (bottom most of the two on the engine shaft?.

The A/C 611 is the same as the Simplicty 4208, 4211.

The adjustmwnt I did not understand at first was the one for the stop on the idler. If not correct it will ride on the belt and cause abnormal wear.

DO NOT ACTIVATE THE PTO, WHEN DECK IS RAISED.

http://bsintek.basco.com/BriggsDocumentDisplay/heCyEN8buO1rE3Cvh5kbp796Dq.pdf

Up around page 22

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Simplicity_728

Both spindles and idler spin freely. I did adjust the belt guides and idler pulley guide how it says in the manual, it doesn't rub. Spindle brakes are adjusted as it says. I did notice a slight bend in the pulley on the engine

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GrincheyOne

That dual pulley assembly engineering is questionable. There is no real key to speak of, and both the pulleys (drive and PTO) are pressed steel (w/virtually no hub to place the pu;;er against). I recently had the "pleasure" of destroying one.

In the midst of swapping engines between my '90 and '88 4212Gs, My attempt to remove the assembly from the '90 engine, pulled the assembly apart and crushed the sheave on the PTO pulley.

REASON FOR SWAP? see...

http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=144107

The second day out on the '88 engine, the governor went "bonkers", until I take it apart over the '15 winter, I will not know the overall damage to that engine. More to come...

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Simplicity_728

I agree with the pulley design Wayne. It seems to be a weak point in these. Do you think it could be straightened? I bought an Allis 808GT a few years ago and I couldn't even mow with it at all because the bottom pulley was crushed. I was surprised to see that the 611 LTD is pretty much the same as the 808GT/810GT/6008/6011/etc except for the peerless transaxle instead of the cast iron 3-speed and advertised as an LT instead of a GT.

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GrincheyOne

IMO To my limited knowledge, there is no simplistic "used on" search capability (available outside of the B&S corporate confines).

How refreshing it would be to enter a part# and see all products where it is used. For example how many part#s exist for something as basic as a 5/16-18 1 inch cap screw across the numerous products.

This particular assembly was/is implemented across many product platforms, EG 3000, 4000, 5000, etc. both A/C and Simplicity, but not to slight other brief manufacturing endeavors.

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powerking_one

Nick,

What were the failure "modes" of the broken belts? Were they shredded/de-laminated across the entire length or were they a clean break? A clean break would suggest a very big/sudden shock load causing this (like a spindle lockup/bearing seizing). A shredded belt would indicate either just normal aging and deterioration or wrong belt type or mechanical rubbing on the front/back side belt path. If the belt just snapped, then maybe there is a "floater" piece of debris in one of the spindle housings/bearings or the idler that locking it up at failure time; intermittently?

Tom(PK)

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timflury

I would guess that there might be a worn pulley, or multiple worn pulleys.

The V groove in the pulleys does wear and then the belt would "Bottom out" in the groove.

Do a Google image search of "worn v belt pulley" and see what I mean.

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Simplicity_728

With 3 belts so far, I've used a dayco, gates, and Simplicity. On each on the fabric coating wore away at the outer edge of the "V" part that rides in the pulley and then it will just break. The rest of the belt looks good otherwise

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powerking_one
quote:With 3 belts so far, I've used a dayco, gates, and Simplicity. On each on the fabric coating wore away at the outer edge of the "V" part that rides in the pulley and then it will just break. The rest of the belt looks good otherwiseid="quote">
id="quote">

Nick, with this being said, I agree with "timflury" that this might a be worn crankshaft pulley or others causing rapid wear of the belt. Since you reference a Simplicity OEM belt also failing, this would be my guess. Below is a youtube video link showing the cheesy stamped steel pulleys manufacturers use now and how when worn can cause these types of belt failures.

You can skip to time index ~~ 3:20 min into the video and ignore the first boring parts.

Tom (PK)

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GrincheyOne

Tom, it would appear to me, that the electric clutch is the driving force for the PTO (?). The drive pulley on this tractor has the same dimpled tube in place of a key, much like the dual pulley assy. on the 611. Note the weld of the pulley to the tube, This is not true on the

pulleys on the Typically NLA #1674163SM, to be found at salvage yards, or JJNemes ($35). [the last I looked].

This is a 4 year old TOPIC thread on the pulley subject...

http://simpletractors.com/Club2/topic.asp?TOPIC_ID=118119

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Simplicity_728

Update for those who helped me out. I bought a used stack pulley in good shape and have mowed my lawn twice with no issues and the belt looks great. It's the smoothest quietest mower deck I've owned. Thanks again everyone

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