I was mowing the lawn over the weekend with my JD LX288 and the grass was a bit long. I was going slow and maybe only doing a 50% - 60% pass to not put as much strain on the engine. About half way through The engine started to lose power and I could see it starting to emit some black smoke. There was also a slight bouncing with the RPMs and not that steady, constant sound with a normal running engine.
I stopped and let it sit for a few minutes, then did a partial oil change, not changing the oil filter but putting in fresh oil. First thing I noticed was that the oil was running like water. The engine was still hot but I thought it should be a bit thicker than it looked like. Not sure if this is normal with a hot engine or not. I drained about 1 quart of oil but only put in 1 quart to replace what was drained and it was in between the fill lines. I took apart the air filter, cleaned the per-filter and paper filter was clean, but it looked oily.
After some time I started it again and it still had the same issues with black smoke and under powered. I thought the issue might be the oil on the paper filter so i took of the air filter and I still had the same issue of the black smoke, under powered and RPMs bouncing. I decided to run the engine without the air filters to see if it might solve or reduce the issue but it didn't seem to help.
This lawn tractor has a B&S 18 HP vertical vanguard engine. I know I need to check the carb this weekend and also find out if this engine has a breather valve and check to see if that is stuck. Worst case scenario would be rings and maybe scoring on the cylinder wall I think.
If it is the cylinder and rings what would be a ball park cost to get this fixed or rebuilt? I am trying to figure out if it would be worth fixing if it needs a rebuild or if I should look for something new(er). I just don't have the time to learn how to rebuilt this myself. Is there something I might be overlooking or other options I am not thinking of?