B&S engine spewing blue smoke all of a sudden

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crw

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Over the last three mowing sessions, my riding lawn mower is blowing blue smoke. It's about 1/3 of a quart for every hour! I'm getting nauseated sitting behind it from all the smoke.

Right now I have new oil (SAE 30) in there. Still doing it.

I took it in to someone... he changed the plug and gave me a inline fuel shut off-valve and sent me on my way. Gee thanks.

He also suggested that if the problem remained (it has), then I would likely need a new or rebuilt carburetor. The theory being (I guess) that the carb is dumping oodles of fuel into the piston and causing some oil to burn in addition to the fuel. Anyway, I'm hesitant to take it back to this guy for fear of getting on a new parts merry-go-round.

What do you think? New carb, damaged engine, or something else?
 
I should have added, there is no evidence of a head gasket leak. And, the problem cropped up "all of a sudden". One day about three weeks ago, the problem started, and it's getting slightly worse during each mowing.

Thanks for any advice you can provide.
 
Did you upend it to clean it ?

Better half did that to my mower, and oil leaked through and saturated the ais cleaner.
 
Well...

How does the engine sound, the same as before or some noises??

Does it run smooth or like the choke is partially on??

I would spray a good carb cleaner or pour Seafoam in with a HOT engine and change the air filter while you're at it.

Then after that, go deeper.
 
Yes, let me give some more details...

No, it hasn't been turned over. Its a riding mower... I have about 2/3 of a acre that I mow weekly.

I cleaned out the air filter already.

Engine sounds about the same. No choke on this engine. I was thinking about carb cleaner or Seafoam... that might be the next step.

My most fundamental question is, would a bad carb cause my engine (17 hp Briggs and Stratton "INTEK") to spew blue smoke? The smoke comes out strongest when the engine is stressed, for example if I hit a patch of thicker grass, the engine will respond to compensate, and at that moment I'll get an extra strong puff of blue smoke.
 
Hummm...

Get that Carb Cleaner or Seafoam in it right away before the next mowing!!

Also, clean and lube all linkage on/to the carb.

Then - Write us in the morning.
 
Does the smoke smell like burning oil? I usually smell an oil burning car before I see the smoke. If its oil, that's probably rings/valves/etc

Since the smoke is visible.... If it is a twin cylinder, you could take the exhaust pipe off and see if both cylinders smoke the same. If so, I'd suspect the carb (since its common to both). If only one smokes, that's an issue on one cylinder (rings, valves, etc).

Do they put valve guide seals on those? If it has overhead valves, you could pull the valve cover and check the valve guide seal, and see the valve guide is broken. Thats kind of a long shot though.

-Joe
 
You've got an oil problem, messing with the carb won't fix it. The fact that it is blue smoke and your oil usage is far beyond acceptable are the key indicators.

I'd re-ring it at a minimum.
 
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I was in a hurry one day with my parents rider. I believe a 16.5 hp Briggs. Checked the oil and started mowing. I was blowing smoke out the muffler/burning oil which had never happened before. Then I saw I left the dipstick unscrewed. Simply screwed it in place and the problem was gone. So, could you possibly have a leak somewhere drawing in air like I had?
 
I had a OHV briggs single cylinder tractor that had the rings
unseat and spin on the piston until the ring gaps almost lined up
vertically. Oil pushed right past them to get burned with the
gas. Horrible smoke. This was on its second season!
 
These small engines in most cases there isn't enough oil to burn to SEE blue smoke visually to that extent. It's a small engine not like car engines.
 
Originally Posted By: crw
Over the last three mowing sessions, my riding lawn mower is blowing blue smoke. It's about 1/3 of a quart for every hour! I'm getting nauseated sitting behind it from all the smoke.

Right now I have new oil (SAE 30) in there. Still doing it.

I took it in to someone... he changed the plug and gave me a inline fuel shut off-valve and sent me on my way. Gee thanks.

He also suggested that if the problem remained (it has), then I would likely need a new or rebuilt carburetor. The theory being (I guess) that the carb is dumping oodles of fuel into the piston and causing some oil to burn in addition to the fuel. Anyway, I'm hesitant to take it back to this guy for fear of getting on a new parts merry-go-round.

What do you think? New carb, damaged engine, or something else?


If you are losing 1/3 qt of oil every hour you got to have a leak...there is no way a small engine can burn off that much oil..do you notice the engine running abnormal . Most time to getting a new carb it wouldn't start to begin with. Unusual!
 
One thing about the dipstick idea... I saw this on another thread, The dipstick screws on, and there is a place on the cap where I think a gasket ought to be... but no gasket is there. That might explain it (maybe) but it doesn't fit the model of why all of a sudden this started happening. Well, there was one time that I took the cap off, and if the gasket went flying at that moment, that might explain it...... (the plot thickens)
 
Vertical shaft OHV engines like this 17hp Briggs Intek will burn oil like mad if the crankcase is even slightly overfilled with oil. Sometimes the method in which you read the dipstick is confusing (inserted, not inserted, etc) Oil will run right from the sump into the cylinder especially when being used or stored nose down. Another problem I've heard of is a bad head gasket pressurizing the sump to the point of blowing oil out the breather, into the carb and out the exhaust. Another possibility like said is a piston ring issue. And yes, if your mower is getting oil in the cylinder you will see blue smoke. Lots of it.

Joel
 
Briggs Intek have head gasket issues.

I had the same issue on mine 18hp Intek. The leak occurs between the valve galley and piston. You can confirm by running the engine with the valve cover off and you'll see oil spraying (stand back) from that area. Good news is the part is < $10 and not a difficult fix. I got instructions/spec from Walt over at the gardenweb forums.
 
Hmmm... that is a thought. Actually, that was my original thought. But when I took it to an "expert", he said that he didn't see anything spraying out, and I made the assumption that something would spray out. But I need to take off the valve cover?

I'm going to stop giving this "expert" my business...

Thanks for the info! If you can think of anything else I should know, please share!
 
I had the same problem with me 02 troy bilt rider. Took the head off and found the gasket cracked between piston and valves. Went to the mower shop got a gasket set, 20 or 30 bucks. replaced head gasket, valve seal, oil dip stick o-rings and cleaned crankcase breather. Changed oil and filter, started up, let it run for a few min. to burn the rest of the oil and all is good. FYI the mower has a 17.5hp b&s inteck.
 
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