MTD / Briggs engine pulley problems

[38racing]

Yes there is a rod to adjust but it's essential that both pulley guards be in place or no amount of adjustment will stop the belt. Been there. There are also brake pads bolted to foot boards above pulleys. I actually added a spacer to lower mine closer to pulley.

[bgsengine]

But the blades are staying partly engaged even at the top. If I pull back on the handle, the blades will stop but once I take the tension off and let it relax into position, the blades start spinning again.

Both belt keeper bolts in place? They typically look like studs with a 5/16 hex on the very end - they'll have 5/16-18 threads, they thread into the frame under engine and stick down close to the PTO section of the engine pulley - When deck is engaged (belt tight) they should be close enough that they do not quite touch belt (or pulley) and when disengaged, deck belt will tend to "round out" and contact the belt guide bolts which causes belt to "pooch" out from the pulley (since it won't return to "round").. In short, should be 2 belt guide bolts (they have to be removed to change PTO Belt)

I found some info on the internet stating that the Rod Disengatement lever needs to be adjusted. I believe it connects to a hole with a pin into the Shaft Assembly Stab per the schematic I was looking at. I believe I need to disconnect it and turn clockwise to cause the deck to move more forward when raised to the top setting. Am I on the right track?

If your belt guide bolts are there and correctly in place and belt still too tight, then yes there is adjustment to compensate for wear in deck- Also, check for wear on the deck height detent bracket - Often there is wear that allows the deck height lever to move forward far enough to engage deck. (The stop should hold lever far back enough that deck pulleys contact the blade brake pads bolted up under fender footrests) so, you may need a PTO / Deck Height detent bracket..... and re-adjustment of that ferrule you mention

I ran it for about 45 seconds before noticing this problem. The pulley got pretty hot during that time, which I'm guessing is due to the fact that the blades were partially engaged causing a whole lot of friction as the belt kind of slipped on the pulley for that time. It was very hot to the touch.

Once I get this done, she's out of my garage....yay!

[lefty]

Belt keeper bolts are in place. One of them was actually bent pretty bad due to the debauchery that occurred when the belt broke. I was able to remove them and straighten the one that was bent. I got them back in shape and installed.

When you refer to the detent bracket, do you mean the notched thing on the side with the different deck height settings?

I was thinking that maybe the old belt was stretched and maybe someone adjusted it in the past to make up for it. And now with the new belt, an adjustment may be in order again.

[bgsengine]

When you refer to the detent bracket, do you mean the notched thing on the side with the different deck height settings?

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Correct - that is also the same lever that engages the mower, no? The "fully up" detent often gets worn (just vibration/hammering/peening) to where it does not fully disengage the deck ( just a bit higher than mowing at highest height setting) so if you pull all the way back on that lever and the deck belt goes fully slack, then you may just need that detent bracket - Part number from memory I think was 783-04113P or something similar . Used to replace 2-3 of those a year when I still would see those older machines come in to the shop.. They've started to become rare to see any more these days though..

[Arkie]

And if all the above does not cure the blade running issue the replacement belt is too USUALLY short. (and will wear out new pulley brake pads fast)
Common problem when the belt is new and little too short and dangerous as heck. Another one of MTD's weak ideas.

Also make sure all the safety interlocks are operating correctly before sending it out the door and do not ever get out of the seat on one of those rigs and leave the mower engine running. I've seen the blades start spinning just from the belt getting warmed up while slipping in the pulley groove.

I've had to sometimes just suck it up and order a belt $$ that is at least one inch longer than spec'ed mainly due to a new belt not being the correct size and usually somewhat shorter. If the belt is little too long before you get a dis-engauge the belt guides have to be in really good shape and adjusted correctly or the belt will nuisance trip off the pulleys.

Due to that MTD design I recommend to the OP that for their safety to get a safer type lawn mower and recommend a electric type blade clutch. (if I designed or built something like that I could not sleep at night)

[KE4AVB]

Boy I haven't seen one those decks in 5 years...Where it is a pain to get the rear pulling deck spring off and on.

As Arkie said check the belt length too. Unless using the MTD OEM belt which appear to be the 954-0439 (though many places are questioning that PN) which is .656 x 60.2, the 5/8 (.625) replacement is usually 60 inches.

If your are using aftermarket belt is a good chance that it is shorter than the spec'd size. Places like Stens will send out belts that are +- 1/4" per their tech support but I have received belts up an inch short from Stens and up to 2 inches from what was my aftermarket belt supplier. It got so bad that I finally quit installing aftermarket belts due to all the headaches I had with them being mislabeled. The belt were good belts just the wrong when measured when to the labeled size.

With all the aftermarket belt problems I was having I ended up buying a v-belt measuring tools with extensions so I measure up to 170". I nearly need to add another 30" extension due to some ZTR belts.

[lefty]

I think that might be it, belt too short I mean. Likely a combination of both as that bracket BG mentioned also looks like it's been around for a while.



So I just checked the specs on the belt and it's 60 inch, so too short. It is an aftermarket under the same part number.

Is the only remedy for this an oem belt? Or can adjustment be made to the engagement rod to compensate for the difference? The blade does disengage when I pull back a little on the lever.


The breaks looked like they were in good shape. I also inspected the one on the deck when I had it off a while back to replace the spindle.

By they way, I just found an OEM online and the specs say 60.2

[KE4AVB]

Lefty, If you look at specs I gave the reason for the shorter aftermarket belt. Its not as wide; hence, the reason it is slightly shorter. The next size I finding in the 5/8 is 60.8" from my vendor which is a Gravely/Ariens belt PN 07235000. Personally if the bracket is still available I try it first since the deck does disengage when the lever is pulled back.

It like me going from a 1/2 to 5/8 belt on my Yard Machines I had to adjust it size by 1-1/2" Which I one a 1/2 shorter and could never engage the deck unless it was fully raise or it threw the belt. I should be now to engage any where since I now finally found a belt in a half inch size. The current mower setup just ate 1/2 decks like candy. That what I get for replacing a 16.5 with 21 HP engine.

[Arkie]

You may know this since you mention the deck dis/engaugement rod adjustment.
Since we do not have a exact MTD model number for reference this OPERATORS MANUAL may not match your machine, but will give you a general idea to make sure the deck stabilizer plate can be checked for slack, worn parts etc.

OPERATORS MANUAL

Transmatic Lawn
Tractors
Model Series
660 thru 679

On about pg 16 of this service adjustment manual note that the rear rod of the decks stabilizer plate for 38 and 42 inch decks must be in their correct holes. (the 38 and 42 inch decks do not use the same holes for the cross rod)

[KE4AVB]

Actually the model was posted in the very first post so it is a 699 (13AS699H088) with 46" deck.

So here is an extract the instructions from the OM of MTD 690-699 series.

https://drive.google.com/open?id=123Sg0BVS4mnnU0gTXjS1ty8X_x7Aq6jK