Lawnmower sputters when engaging pull assist

MerlinsBeard

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Hi, I'm new the forum and am a little handy but not a small engine guy by any means. Trying to see what the next step in troubleshooting is.

I have a 10 year old JS36 John Deere push mower that I have been having issues trying to fix a recurring intermittent sputtering problem where it wants to stall out. The problem started two months ago and has progressively gotten worse. If the sputtering occurs, if I raise the mower deck by pushing down on the handle, the mower revs back to life.

The main recommendation was to clean the carburetor. Up till this point, I've replaced air filter and spark plugs yearly, oil 1 to 2 times a year, and run the gas out at the end of the season. I tighten up bolts and the normal maintenance stuff in the John Deere manual.

To clean the carburetor, I followed the steps from Steve's small engine saloon youtube channel performing everything but the needle seat replacement, making sure to get the inlet jet on the bolt. However, when I put the carburetor back on, the problem was less consistent but still happens where it sputters and wants to stall out. The fuel drains from the drain line fine. There was a decent amount of soot looking grit in the bowl but as far as I can tell the carburetor is clean.

Eventually I realize that the issue doesn't happen at all when I pull the mower backwards, or I disable the pull assist. If I lock the push mower handle and don't use the pull assist, I do not have any discernable noise or stall symptoms.

I don't really know where to start next for troubleshooting. I can try to replace the pull assist belts, drive cables, others, but I don't have a good intuition as far as what's causing this.

I know that the pull assist has gotten "weaker" but there is still a perceptible difference between engaging and not engaging, especially when going up hill. It hasn't bothered me so I haven't attempted to replace the belt or cable. Technically I can still mow without the pull assist, but would prefer to try to fix it if possible if there's a link between the pull assist and stalling the engine.
 

MerlinsBeard

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Aug 21, 2022
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Just to give an update. I mowed the lawn without the drive assist and had no sputtering or stalling issues. I engaged the drive assist on concrete with no discernable symptoms. It's only the combination that leads to stalling the engine.

I'm planning to pursue transmission replacement if I can get parts. Anyone repaired or replaced these drive assist transmissions before? I don't have super mechanical intuition, so just wondering if I should leave this to someone who is more of a pro. I can usually follow along a youtube video and get by, but without it, I can get wrapped around the axle with these kinds of things.
 
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