# L120 Surging



## L120_Atlanta (Aug 23, 2012)

I have an L120, 5 or so years old. It has about 100 hours on it. Our yard is no more than half an acre, but I have a ton of pine trees so I wanted something to cut and vacuum up as many of the cones as possible. Figured the extra HP would have no problems generating a lot of lift for that and it works great for me. Point being the mower gets reasonably light use.

A couple of weeks ago, it wouldn't crank. Turned over fine, but no spark, never "hit" once. Battery was well charged and I recharged it just to be certain; no help. In looking about to see if I had fuel, I did clean out the air filter and whatnot, but there were no issues found.

Put it back together. Began to suspect under-seat kill switch. Fiddled with that and it cranked up, but suddenly the engine, once warm and with choke off, began to surge.

Full throttle or partial (though more pronounced at full throttle) and in gear/driving or idling, even with the blade engaged briefly to test, the engine speed rises and falls significantly, in a VERY regular rhythm. The cycle is around 2 or 3 seconds. Hard to describe-- almost a "galloping" feel, if that makes any sense. After sitting a long while, it did stall, but a restart returned engine to same state.

Nothing known changed from before to after surging except air filter came off and went back on, and the under-seat kill switch was wiggled and tapped at a bit. No fuel added, for example. Inside the filter there was no trash or debris, so I cannot imagine anything dislodged.

I'm not quite certain what to look at next. Hate to take to dealer and wait forever, then spend a fortune. Does any of this point to a known concern?

Thanks!


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## camaro76 (Aug 8, 2012)

My 318 also had a surging problem. I went through the tractor. Eventually I found two things. In my situation the float in the carburetor has a brass stem that the float rests over top. The stem is not a round piece but more of a square stem. The flats are actually grooves. Hope this makes sense. This brass stem was worn out of shape not allowing the float to move freely. This allowed the engine to surge. My tractor is a hydrastat. The lever that moves the tractor forward and reverse has spring steel that holds the lever against a neutral safety switch. The steel had lost some of its spring action and wasn't pushing the lever fully in to the switch. When the tractor was running with the brake set and the driver would get off the engine would stall because the neutral safety was not fully engaged by the lever.
I would look into the carb float first. Possible you could have dirty jets or worn seats.


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