Oil in carb, B&S 4HP Quatro on Poulon lawn mower

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  #1  
Old 06-25-09, 03:49 PM
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Oil in carb, B&S 4HP Quatro on Poulon lawn mower

I recently adopted a "rescue" lawn mower, and cleaned it up, changed the oil and carb diaphragm, etc.--and it ran beautifully for two mowings of the lawn.

The next time I started it, I was greeted with a huge cloud of blue smoke. I found the foam air filter soaked with oil, and oil in the carb. I cleaned it all up, then ran it for a while, and it was great. A few days later, I started it again--and the same story, blue smoke. Not as much oil in the filter, but still there. And when I ran it with the filter off and the breather tube disconnected, it ran cleanly.

It's a Briggs & Stratton model 10A902 engine.

Any suggestions on where to start? I see where the breather tube comes out near the carb, but have no idea how to go about checking the valves, etc.

Thanks.
 
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  #2  
Old 06-25-09, 04:31 PM
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Oh, I should add--the oil is exactly at the full mark on the dipstick.
 
  #3  
Old 06-25-09, 04:33 PM
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It sounds as though it is over full on oil or it is running too fast and blowing oil or it is being tilted to a position where the carb is not on the up side. Have a good one. Geo
 
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Old 06-25-09, 04:37 PM
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Originally Posted by geogrubb View Post
It sounds as though it is over full on oil or it is running too fast and blowing oil or it is being tilted to a position where the carb is not on the up side. Have a good one. Geo
Negative on the over-full* and on the being tilted with carb under. Running too fast...I don't know how fast it's going at full throttle, but this happened at low, also.

*It's full, but right at the high mark on the dipstick.
 
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Old 06-25-09, 07:15 PM
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Sorry about the overfull, if you check the posting times, you were posting and I was typing. Have a good one. Geo
 
  #6  
Old 06-25-09, 07:36 PM
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I think a Briggs & Stratton model 10A902 engine is the one with the carb setting on top of the fuel tank and the air filter sets on top of that for oil to get in the air filter would require some blowby pressure from somewhere. The engine should run between 2800 and 3200 rpm above that it could start blowing oil or it might have a partially sheared flywheel key which would affect ignition timing and have it firing with valves open. Have a good one. Geo
 
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Old 06-25-09, 08:43 PM
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Originally Posted by geogrubb View Post
I think a Briggs & Stratton model 10A902 engine is the one with the carb setting on top of the fuel tank and the air filter sets on top of that for oil to get in the air filter would require some blowby pressure from somewhere. The engine should run between 2800 and 3200 rpm above that it could start blowing oil or it might have a partially sheared flywheel key which would affect ignition timing and have it firing with valves open. Have a good one. Geo
Yes, that's correct about the setup, although I think the fuel tank is more to the side of the carb, but at a lower level.

I have an old car tachometer for 4/8 cylinder engines. Any reason I can't use that to check the RPM on the 1-cylinder? I had to bend the throttle tang some, and I may have bent it too far to too high a speed.

What puzzles me about this is that it ran so well the first couple of times, and then after sitting for a few days suddenly started blowing oil from the moment of startup.
 
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Old 06-26-09, 08:43 AM
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If the tach is a battery powered one that you hook to the distrubator, no, it wont work... Did you use SAE 30 oil??? If the oil is too thin, it may push thru the breather,, Also if the cooling system is blocked with grass under the shroud (or really greasy) It could overheat & thin out the oil.... Does the engine sound about as fast as your neighbors??? Roger
 
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Old 06-26-09, 09:44 AM
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Originally Posted by hopkinsr2 View Post
If the tach is a battery powered one that you hook to the distrubator, no, it wont work... Did you use SAE 30 oil??? If the oil is too thin, it may push thru the breather,, Also if the cooling system is blocked with grass under the shroud (or really greasy) It could overheat & thin out the oil.... Does the engine sound about as fast as your neighbors??? Roger
I used 10-30 oil, I believe. If by the cooling system you mean the cooling fins, they're not dirty or clogged. I think it may be a little fast at full throttle, but certainly not bad at low throttle. I'll tweak it down a bit. But...

Here's the thing. It ran perfectly, without any smoke, while I mowed the lawn. No indication of overheating. Then it sat. And while it sat (apparently), oil oozed out and soaked the filter, and dripped into the carb. Because the next time I pulled the cord--boom, cloud of smoke.

Now when I try again, I clean out the oil, I start it, it runs fine. But after about thirty seconds, the smoke starts billowing out again.

Any tips on how to check the breather system?

Should I be thinking about checking the head gasket?
 
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Old 06-26-09, 12:40 PM
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The smoke you are seeing may be from oil setting in the muffler from when it initally blew the oil, let it set and run at low speed for 15-20 minutes to give it a chance to burn away the oil. Have a good one. Geo
 
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Old 06-26-09, 12:51 PM
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I agree with geo however, if it is still puffing pretty good after3-5 minutes I would stop and check the oil. If the level is good then continue, just make sure the oil level is not dropping.
 
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Old 06-26-09, 01:03 PM
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I'll give that a try. However, I am wiping oil out of the carb, and the breather tube connection is oily. Maybe I'll try running it a few minutes with the breather disconnected from the carb, and something to soak up the oil if it's coming out of the tube.
 
  #13  
Old 06-26-09, 04:43 PM
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""I recently adopted a "rescue" lawn mower, and cleaned it up, changed the oil and carb diaphragm, etc.""

I kinda hate to say it,,, But maybe it was a ""Rescue"" lawnmower because the previous owners had issues with it... It may have worked 'till the new oil washed all the crud from the inside of the engine... I don't know if that is possible,,, But people have told me that.... If this is the flat-head engine, It won't be a head gasket issue.... Roger
 
  #14  
Old 06-26-09, 06:50 PM
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hopkinsr2 makes a good point, sometimes what you see is not what you have. All the mowers I work on are "rescue" mowers and since they are going to be given away I have, "when necessary", mixed and matched parts to get a working mower. since the shroud says 10A902 check around breather tube and governor to see if any sheetmetal work has been done, this is the only area of the shroud that I am aware of that would be modified. Have a good one. Geo
 
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Old 06-26-09, 08:59 PM
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I think I've solved the mystery.

I checked the muffler, and no oil in it. I ran it with the breather tube disconnected, and put my finger over the end, and felt a slight vacuum. No oil coming out.

I wiped everything clean, and--to be sure--I wrapped the foam air filter in multiple layers of paper towels and squeezed it like Superman making a diamond from coal. I was surprised how much oil I got out of it--well, not a huge volume, but still enough to wet the paper--and got the filter good and dry. Put everything back together and ran it.

Mowed the lawn, in fact. It ran great. No smoke. No oil evident when I took it apart afterward.

Here's what I think happened: I followed the manual's instructions to clean the filter in detergent, then semi-saturate it in oil and squeeze out the excess. I did squeeze it out, but perhaps not enough. So it ran fine. Then it sat, and I think the remaining oil gradually settled to the bottom of the filter and soaked the bottom layer. Then it seeped right into the carb. I did, on further testing, squeeze more oil out of the foam, but I never really tried to get all of the oil out--until today.

I think the oil was from the filter itself. Maybe even the oil that was on end of the breather tube, as that's under the air filter.

I'll find out, I guess, when I try running it again in a few days. But I think the whole problem was too much oil on the filter in the first place.
 

Last edited by starrigger; 06-26-09 at 11:42 PM.
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