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OK, I've a B&S engine on a Craftsman mower. The engine is model # 128602 0304 E1. Got the unit off of Craigslist, because it would not run. Got it home and cleaned it up, and got it running (pretty easily). Had a serious vibration, so looked at the blade and it is evident the blade hit something, as it was bent on one end. Put on a replacement blade, and everything smoothed out and runs fine....BUT, it has spurts of intense oil smoke when running.

When I tipped the mower, the Carb side was up. Is it possible I got a boatload of oil into the intake or muffler and it is burning off? Or, possible loose valves? As an FYI, I am running 5-30 in this mower, and can easily put in plain 30 weight...in fact, that would probably be good, as the 5-30 could be a flush oil...

Need some wise opinions to proceed...

The breather assembly is behind the muffler, so it is very likely that you will get oil through the breather system into the intake which is then burnt.

ILENGINE said:

The breather assembly is behind the muffler, so it is very likely that you will get oil through the breather system into the intake which is then burnt.

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Thanks ILENGINE. I plan to pull the air filter, muffler and breather assembly tomorrow to see if that is the issue.

OK -- Pulled the air cleaner, muffler, spark plug and oil breather. The only indicator of oil burning was on the plug. Put it all back together and cranked it up and still smokes a-plenty. My sense is a blown head gasket. Before I head to the local vendor tomorrow to see if they have a gasket in stock, any other suggestions from the group?

Thanks very much!

Gsnod said:

OK -- Pulled the air cleaner, muffler, spark plug and oil breather. The only indicator of oil burning was on the plug. Put it all back together and cranked it up and still smokes a-plenty. My sense is a blown head gasket. Before I head to the local vendor tomorrow to see if they have a gasket in stock, any other suggestions from the group?

Thanks very much!

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Well, pulled the head on this engine today and replaced the head gasket. Mowed a bit with it and still burning oil. Even changed to a heavier oil (15-40) and no change. I'm guessing bad rings on this 2004 motor. I guess the only way to really find out is to get a compression gauge and go from there....

Anyone have any more suggestions?

ILENGINE said:

The breather assembly is behind the muffler, so it is very likely that you will get oil through the breather system into the intake which is then burnt.

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ILENGINE -- can you give me an idea of how to test whether the breather assembly is working?

Thanks very much! :thumbsup:

There is not really a test for the breather assy. The spec is if you can slide a .040 wire feeler gauge between the disc and the body, it needs replaced. What happens a lot is people tip the mower on its side with the carb facing up, and because the breather is now on the bottom oil fills the breather, and then when set back down on the wheels, and then immediately started, it pushes the oil over into the carb, which is then burnt.

ILENGINE said:

There is not really a test for the breather assy. The spec is if you can slide a .040 wire feeler gauge between the disc and the body, it needs replaced. What happens a lot is people tip the mower on its side with the carb facing up, and because the breather is now on the bottom oil fills the breather, and then when set back down on the wheels, and then immediately started, it pushes the oil over into the carb, which is then burnt.

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How does one slide a feeler gauge to check the spacing... -- between the sides?

If you remove the breather assy from the engine, there is a round disc that seals the crankcase and lets the pressure out. The disc moves in slightly to allow pressure to escape the crankcase, You take a wire type feeler gauge and slide it under the edge of the disc and make sure there isn't excessive clearance. I haven't seen one fail though. I have pulled a few over the years, and the disc would be gone though.

ILENGINE said:

If you remove the breather assy from the engine, there is a round disc that seals the crankcase and lets the pressure out. The disc moves in slightly to allow pressure to escape the crankcase, You take a wire type feeler gauge and slide it under the edge of the disc and make sure there isn't excessive clearance. I haven't seen one fail though. I have pulled a few over the years, and the disc would be gone though.

Click to expand...

Thanks (again) ILENGINE for your guidance. Here's what I've done to try and determine the cause of the smoke (which is bluish and smells like burning oil):

1. Air Filter is clean
2. Oil level is OK
3. Changed Head Gasket
4. Confirmed that crankcase breather is good and working.
5. Ran the engine without the muffler....still plenty of smoke.

Any other suggestions before I simply try and get rid of this machine?

A note on 5w-30 I run in my Intek 24. The engine will use the lighter multigrade. After top up and 2 hour run the sump is typically down2-3 oz. My take is the thinner oil is cooling better and also getting past the rings but not smoking. Yesterday (93F) the Intek sump oil was 300F for a short while but held 30 psi with this Chevron oil.