I have recently been fighting a surging issue with my White LT 542G riding mower. The details on the mower and engine are as follows:
Tractor model #: 13A2771G790 (March 2006 mfg date)
Engine model #: OV490EA (Tecumseh) -- It's an 18 hp engine.
The mower will start normally, but then used to just completely cut out and die. It would start right back up immediately afterwards and I could use it as normal...or so I thought.
I originally (over a year ago when the problem was intermittent) thought the problem was due to a faulty fuel solenoid in the carb, but replacing with a new one did not help cure the issue. There is a thread over on MTF that I started a while back that has some more info that might be helpful. Here is the link: White LT542G Runs Briefly, Then Dies
More recently, I reacted quickly enough and moved the throttle control back and forth as it started struggling and I was able to catch the motor and prevent it from dying. However, the motor would surge badly at full throttle, and now will not allow me to engage the blades without completely shutting down. I can watch the governor at all throttle speeds and it will almost randomly start moving back and forth, though I don't always hear the rpm change when it does so, unless the surging starts.
I pulled the carb today and cleaned it (though I probably should go back in again as it made no difference). I replaced the fuel filter as it had been a while.
Things I observed as I was cleaning the carb and reinstalling:
1. The choke does not always open back up when the throttle cable is moved out of that position (I only observed this when the engine was off...did not get down and check while running).
2. When the throttle control is set as low as it goes, the throttle butterfly in the carb is not all the way closed. In fact, the portion that sticks out above the carb and can contact some sort of stop screw never actually contacts that stop screw. Not sure if my description is even close to adequate on that one...
So...I can understand that the engine is running lean, from what I have read up on so far, but really am not sure where to go next to try and solve this issue.
Really hoping it's not something wrong with the governor assembly in the engine itself.