I received a 4 to 5 year old MTD Yard-Man model 573 lawn mower with a Tecumseh LEV105-347005B engine in a swap. The previous owner did zero maintenance - the air filter look liked it had never been changed, the oil was gray black and thick, and the blade was blunt. The mower would barely start and would not stay running or run correctly - it would hunt badly. Some wheel height adjustment parts were missing.

So far I've cleaned the carb twice; replaced the carb bowl washer and o-ring; adjusted the carb float level; replaced the spark plug (checked the gap), air filter, and inlet gasket; changed the oil twice (the first oil was gray black after 2 hours of operation); Sea Foam'ed the gas and the air intake directly; used new gas; fixed the height adjustment; sharpened the blade; etc.

Now it runs almost, but not quite, perfectly. It starts on the first pull and runs well, but when cold for the first few minutes it will sound like it misfires. The misfires happen a few to 10 seconds apart and tend to be two or three in a row. However after the first few minutes when the engine is warm the misfiring stops completely and the engine runs smoothly with no detectable issues. The misfiring is not enough to cause a stall of any major issue with cutting grass.

I was wondering if the flywheel key might have been bent causing a slight misadjustment in the timing. Then as the engine warms up this slight offset is not an issue.

Could it be anything else?

Also I'm also hoping the oil condition is not indicative of something more serious in the engine. I expected the first oil to get dirty from loosening all the crud from the previous non-existent servicing, and probably the Sea Foam. If this new oil also gets dirty as quickly there may be another issue.

Some times when cleaning the bowl nut the small hole about mid way up gets missed, refer to the photo below. Have a good one. Geo
http://i190.photobucket.com/albums/z120/geogrubb/tec_bowl_nut.jpg

I didn't see that 2nd hole, so if this model has one it was not cleaned. Thanks, I'll need to drain and check that.

Finally got to drain the carb and clean out the upper small hole that I missed. Unfortunately it did not help. The engine still skips intermittently and every few seconds for the first few minutes when it is first started. Once it warms up it runs perfectly. There must be some other very minor blockage in the carb that I cannot clean out. I still need to check the flywheel key, however since the engine runs correctly at any speed just above idle even when cold I'm fairly certain it is a carb fuel metering issue.

The other issue is that the oil is jet black after 4 hours of operation. It is probably still cleaning out the junk from the years of lack of maintenance from the previous owner. At least now the black is just soot and there are no visible particles in the oil. I'll change it after the next time and am hoping the oil starts to look more normal.

At this point since it runs well except for this minor skipping I'll just use it, unless anyone has any good suggestions.

add a little Seafoam to the fuel , change the oil and use it :thumbsup:keep us updated