Small engine repair question


Andy writes: If someone can suggest a better newsgroup for this question I would appreciate it..
I have a Briggs 4 cycle , 5hp outboard motor that sat unused for 6 months.
Now, when I crank it up, it runs, but after about 15 seconds oil comes pouring out the oil filler cap at the top of the engine, and after a few more seconds, the engine stops. No noticeable smoke from the exhaust. While the engine is running, but when I crank it back up 15 minutes later , there is some smoke, a small amount, out of the exhaust for a few seconds.
The oil level is proper, and the oil filler cap does not fit tightly, so the oil can come out.
Does anyone have any suggestions ?
Andy in Eureka, Texas
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On Thu, 05 Aug 2010 13:28:18 -0700, Andy wrote:

Might help to know the model number of the motor. Besides that, there may be a separate breather somewhere that an insect or small animal has clogged while the motor was stored. I can't recall ever seeing oil forced up the filler on a small motor but there's pressure building up inside and the only way out it seems is the filler. Usually the right oil level does permit some blow-by to escape up the filler since there should be a small gap at the top of the filler hole in the block between the oil level and the top of the hole. Are you sure you don't have too much oil in it?
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I'd consider this: disassemble slowly. Look for additional crank case breather, and make sure it is open. Remove float bowl, and flush. (I know that doesn't have anything to do with your oil problem, but that will be your next problem.) Drain oil by taking out drain plug. Drain gas by tipping or by taking the gas hose loose. Make sure everything is clean, and that includes the flywheel. They can get wasp nests in there or insect nests, and screw up the spark making apparatus. Just make sure you take it apart enough to see the obvious. Refill with clean oil and gas. You might want to flush the engine with diesel, if you want to take that step. I would. Just drain it really good, and then only use the oil used in the first change for a short interval before changing. If there's an issue with blockage, the diesel should force through and blow it out. Just take the spark loose and tape over the cap. There is little chance of ignition with the diesel fuel, but do be careful. You might try taking a 1/2" drive socket on the big nut on the flywheel and turning the motor for ten revolutions or so to pump the diesel through any channels in there, then drain immediately. You got something blocked, apparently.
Let us know if you find the smoking engine. Errrrrrrrr smoking gun, that is. ;-)
Steve
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My guess is there is too much oil. This could be from gas leaking thru the carb and into the crankcase past the rings over the 6 month period. This will give you a gas/oil overload. Also make sure you have the correct dipstick.
Drain the oil and replace with proper amount as per manual and see what happens then.
Hank <~~~~just guessing
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5 HP engines typically take 16 to 20 ounces of oil.
I'm also thinking crankcase breather. Clogged, jammed, etc.
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Stormin Mormon wrote:

My bet is a spider found it's way in there and built a web.
Jon
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Andy wrote:

Oil cap don't fit? Is it supposed to be tight or is it a breather cap?
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Andy comments
Thanks to all for their advice.
B&S only makes one model of outboard motor.
As I mentioned, the oil level is correct.
The oil filler cap is NOT a tight fit. It never has been. The dipstick is part of it and it is the original issue.
The engine has splash lubrication just like a lawnmore engine, so there are no "channels" to get clogged.
It worked fine when I stored it 6 months ago.
There is no reason to suspect that it has anything to do with wasps nests under the flywheel or leaves in the cowling.....Those would cause more of a cooling problem, and it isn't running long enough for the engine to get hot.
I think I will take off the cover of the crankcase breather and soak it in gas for a while.
If that works, I'll report back here so we all can see if that was the solution.
Andy in Eureka, Texas
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It has a breather and a breather tube. Somewhere that is probably clogged. Typically the tube goes back to the carb or air filter.
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On Fri, 06 Aug 2010 01:12:04 -0700, Andy wrote:

Hmm, the ones I've seen have splash lubrication for the piston, crank etc. - but there are still a couple of small channels between the flywheel end bearing and the valve chest, and then from the valve chest down into the sump. I do think it's unlikely that they'd get jammed though - or if they did, that it'd cause the problem you're seeing.

Or just loosen it where the breather/filter bolts to the engine (for the larger engines the breather also forms the valve chest cover, but that may not be true on yours); you won't make much of a mess in just a few seconds' running.
If you do clean it, test by blowing through it...
cheers
Jules
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On Aug 6, 7:30am, Jules Richardson

Many B+S engines have a breather tube that goes from the crankcase back into the air inlet of the carburetior. The tube is long enough that unless the piston bypass is very large, actual oil doen't make it into the air inlet. If the breather tube is blocked for some reason, the bypassed air around the piston will force oil back up the filler tube.
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