OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines B&S excessive oil in air cleaner box

Hi all,

I have a Briggs & Stratton 5HP (Model Series 124800) which needs a work, but still runs. It is blowing black smoke. I am tying to rectify this by cleaning the carbon build up on the head, adjusting carb, new air filter etc.

I have noticed there is excessive oil in the air cleaner box. It is coming from the breather assembly tube. I have not disassembled the breather assembly to investigate, however does anybody know if this a symptom of something seriously, or if it is a easy fix.

Thanks in advance.

Regards
CC

Is the oil overfilled?

Did you tip the engine exhaust side to the ground then shortly afterward try to start it?

Either one could cause excessive oil to blow through that tube.

CC remove the cover and give it a good clean out as sometimes you get dirt in the breather valve in the cover.

Joe,

The oil isn't overfilled. Although I did tip the mower to the exhaust site, however I didn't start it.

Should I clean out the breather assembly, or just monitor it?

thanks
CC

CC Clean the valve cover breather and see what happens.

If the crankcase ventilation system (i.e. breather) is the source of the oil, you need to attend to that system item by item to see why it is happening. If the source of the oil was the intake manifold, the situation would be much more serious - probably a major mechanical failure. However there would then be wet oil in the combustion chamber. Black smoke in the exhaust is usually a result of rich mixture, while blue smoke is caused by oil entering the combustion chamber. It sounds as if the oil flooding from your breather has clogged the air cleaner, obstructing the entry of air into the engine and causing a massive vacuum in the carburettor venturi, resulting in ultra-rich mixture. You can check this by starting the engine without the air cleaner. If the black smoke ceases, you have found its cause. Fix the problem in the breather system (whatever it is) then wash and re-oil the air cleaner element if it is the foam type.

Joe and Bruce have told you the most likely causes of the breather system problem.