14.5 HP Briggs blowing lots of blue smoke

factorypilotJuly 2, 2010

Mom's rider is blowing blue smoke within 5 min. of starting. Runs normal then acts like somehow a oil line has been allowed to open direcly into the cylinder because the blue smoke could be used by the military as a cover for defense. No need to say engine then runs rough.

Crankcase has normal oil level. I took breather ( I think it would be called the breather) off and opened it up and cleaned it hoping it would help. The fiber disk moved freely. No improvement. Adjusted valves late last sason because of hard starting and ran fine afterwards and until recently.

Engine starts fine and seems to have normal compression.

Need some advice please.

Engine is a model 287707 type 0224-01 single.

Thanks all.

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mownie(7)

Gravity fed fuel system or fuel pump on the mower?
If it has a gravity fed system, and there is no manual, inline fuel cutoff valve (or the valve is not being turned off when the mower is stored) the carb might be leaking some fuel into the crankcase. After 5 minutes or so of running, the fuel will begin to boil off and pressurize the crankcase. The pressure will vent out of the crankcase through the breather, carrying oil mist with it. This mixture then gets burned in the combustion chamber to the tune of a lot of smoke.
Has it done this every time you try to run it lately, or just one time?

    Bookmark   July 3, 2010 at 1:14AM
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walt2002

IF shutting the gas off when engine isn't running doesn't clear up the problem, think head gasket.

Walt Conner

    Bookmark   July 3, 2010 at 8:29AM
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walt2002

You should be checking the oil before starting the engine anyway and gas contamination of oil is going to show over full.

Walt Conner

    Bookmark   July 3, 2010 at 8:31AM
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mownie(7)

Ditto what Walt said about ALWAYS checking the oil before you start the engine. If the oil appears even a little bit higher than it should be, and you know it was not that high before......you might be seeing evidence of a leaking carb if it has a gravity fed fuel system. It does not take much gas in the oil to cause the boil off issue to occur.

    Bookmark   July 3, 2010 at 11:23AM
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factorypilot

It's doing each time she tries to use it and also for me when I took a look at it. I wasn't sure of oil contamination with gas so I changed it and it still smoked shortly (5 or so minutes) after start up.

She does check oil before use, but its hard for me to keep tabs on just how much oil she is adding, but it was at normal level when I checked it.

I admit I didn't pay to much attention as if it is gravity fed or runs a fuel pump. Guessing I would say gravity fed and I did not notice a fuel leak around the carb. It does have an electrical connection on the carb bowl if I remember right that I don't understand what it controls? I live 60 miles away and my memory isn't what it use to be.

It will be a few days before I get back up there and I might bring it back to my place to work on it.

Based on this info, if it supports any other ideas let me know please.

Thanks.

    Bookmark   July 3, 2010 at 3:00PM
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walt2002

Even if it has a fuel pump, IF the gas tank outlet is above the carb inlet, it can leak gas thru the carb. You will not see anything outside courtesy of your friendly EPA. They figure it is better to ruin your engine than leak a few drops of gasoline on ground.

That solenoid on the bottom of the carb shuts the gas off to the main metering jet to help prevent "after fire", does not shut gas off from leaking thru carb. The solenoid MUST have 12 V to it to open it to run. You should hear it click when the ignition switch is turned on.

Walt Conner

    Bookmark   July 3, 2010 at 4:26PM
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factorypilot

I brought the mower home but before putting it on the trailer I checked the oil level and it hasn't increased in the past couple of weeks its benn sitting with the fuel on. I did notice an accumulation of an oily residue in the base of the air filter housing.

Since it doesn't appear that fuel is migrating into the crankcase, should I start with the head gasket? Something else first?

It did smoke very slightly at start up but not a concern. Didn't run it long enough to see if it was going to make a smoke cover though.

Thanks.

    Bookmark   July 18, 2010 at 9:58PM
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walt2002

" I did notice an accumulation of an oily residue in the base of the air filter housing. "

Your symptoms AND what you said above is a fair indication that the head gasket is blown. They always blow between the cylinder and push rod gallery so this pressurizes the crankcase blowing oil into air cleaner box and sucking oil into cylinder. Head gasket about $7.

I have detailed instructions on valve adjustment which will include head bolt torque and pattern. You can probably download a free Service Manual at http://www.mymowerparts.com/pdf/

Even then, my instructions have some pointers not included in the Service Manual. IF you want them, Address below, put in proper format and remind me what you need.

Walt Conner
wconner5 at verizon dot net

    Bookmark   July 18, 2010 at 10:24PM
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factorypilot

Thanks Walt, I may have the info but if I don't I know who to ask!

    Bookmark   July 19, 2010 at 8:47PM
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factorypilot

Walt, It looks like you were on the money with the head gasket. Only evidence of problem was where you mentioned. I replaced it this afternoon and ran it for 20 plus minutes with no problems, which was more than long enough to get it smoking before. Thanks.

One other issue that I might want to address is a extension that was put on to help drain the oil. It is a pipe threaded peice that appears to be seeping a small amount of oil. I snugged it up a liitle but still has a few drips. Do I dare wrap some teflon tape around the threads? Right now I'm a little worried about the intregity of the threads. It's where the drain plug would normally thread into the case.

    Bookmark   July 20, 2010 at 10:55PM
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walt2002

"Do I dare wrap some teflon tape around the threads?"

No problem, you may want to wait until time to change OR tilt the mower over 45 degrees or so to clear oil drain hole.

Walt Conner

    Bookmark   July 21, 2010 at 10:45AM
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factorypilot

Thanks to all that responded to my questions. I decided to wait to the fall oil change to address the oil drain problem.

    Bookmark   July 22, 2010 at 8:34PM
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