Open airbox. Remove filter. Check for dirt on the engine side of the filter.

If there's dirt in the intake throat on the engine side of the filter either the filter was not installed properly or you have one of the airbox challenged B&S twins. There are threads all over the net about B&S twins with airboxes that let dirt through resulting in high oil consumption and/or blown engines. IIRC there were three airbox revisions.

If you have one of the effected engines you may get it covered under warranty directly through B&S, not Sears, if you are persistent and polite.

I have searched the threads and am familiar with the 'airbox' problem. Right now this Intek intake area is very clean and the air is being filtered properly. I am the second owner, so I cannot be sure how it was treated in the past.

What I would like to know is what are the possible causes of this smoking. Are there any other faults, other than 'dirt' damage that would cause the high rpm smoking? Also, how can I determine, for sure, that the damage you mention has actually occurred?

Thanks,

Mike

Gravity fed fuel system or fuel pump fed???
If gravity fed, suspect fuel leaked into engine (past piston rings) while tractor is stored. As engine warms the fuel (if present in crankcase oil) will evaporate (boil) and the venting fumes will transport oil mist past the crankcase breather to be inhaled and burned in the combustion chamber.
Because some oil will pass unburned into the exhaust system, that deposited oil/gunk will cause some smoking until it burns off.
So don't overlook any possibilities.

Oil gets into a combustion chamber either from the top down (valve guides, valve guide seals, head gasket oil leak to chamber)) or from the bottom up (worn or cracked or glazed piston rings, piston or bore wear or glazing, or excessive clearance in bore). High RPM oil consumption (smoking) is generally caused caused by excessive top end wear or a failure of a top end part.

It is that simple.

Since you are the second owner you can't account for the treatment the engine received until you owned it.

If I were you I'd contact B&S with engine serial numbers at hand and see what they will do for you. Don't be passive. B&S will replace the engine if you make a good case and they feel you are sincere and a loyal B&S owner.

Mownie and Justalurker....thanks for the help...

Mownie...Engine is fuel pump fed, so I don't think gas drained into the crankcase. Have also changed oil and filter. However, I will check the muffler out for oil sludge accumulation.

Justalurker...If, as you say: "High RPM oil consumption (smoking) is generally caused caused by excessive top end wear or a failure of a top end part. ".... then what top end wear or failure should I look for. I adjusted the valves (valves were very close to perfect before adjustment...only loose by about 1 to 2 thou) and everything 'looked' fine. Any suggestions on how I could further isolate the top end wear or failure?

Mike

I said "wear" not out of adjustment.

The wear you're looking for requires dis-assembly and a session with feeler gauges, micrometers, calipers, and bore gauges along with technical engine knowledge and the a fore mentioned measuring tools and the skill and knowledge to use those measuring tools. You're dealing in thousands of an inch... a little beyond DIY.

You check valve guide seal condition and pliability, valve guide to valve stem clearance, ring condition and gap and fit in piston ring lands, bore for round and piston to bore clearance, and piston condition among other things.

If you are smart you'll contact B&S as I said to do.

OP - is the smoke color a dark brown/black or a lighter gray ?

"Vintage: about 2004."

Your code number will tell you what year the engine is, first two numbers.

I can not imagine that B&S is going to warranty a 6 - 7 year old engine.

Compression is good making out of round or excessively worn cylinder unlikely in my opinion. This engine has a passive compression release system so 130 lbs. with that is good. Broken oil ring, maybe although BOTH being broken is also unlikely.

ALWAYS check oil level before operating engine that day. Note that HIGH oil level for no apparent reason is as bad a sign or worse than low oil level.

IF the gas tank is above the level of the carb fuel inlet, it can still siphon gas thru a fuel pump.

You should be able to download a free Service Manual for this engine at - http://www.mymowerparts.com/pdf/ check that crankcase breather is working properly, what you called the PVC valve I think.

Walt Conner

There are far more surprising things than anyone can imagine...

I'd think that B&S wouldn't warranty a 6 or 7 year old engine either EXCEPT that they replaced an engine (at no charge) for a neighbor 6 months ago that had one of the airbox challenged twins in his Sears GT from 04/05.

There wasn't a recall but it is an acknowledged problem and when you call and say the right things they seem to cover the engine replacement either under warranty or simply as gratis. They refer you to an authorized B&S service facility and if they find the right things you get a brand new engine installed at no charge. I've run across other people who have tell the same story regarding their long out of warranty Sears GTs getting new engines at no charge.

What does it cost to call an 800 number Walt... about the same as it costs for any advice the OP will get on any forum?

I don't see where the poster described the smoke color or if there was a consumption problem. Sears bought their engines w/o manufacturer warranty to save a few bucks. Unless that has changed and I missed that fact. Seven years, second owner, no airbox problem- sounds like lots of customer pay teardown if it seemed internal to the OP...

B&S stood the cost of replacing lots of engines in Sears L&Gs that were out of Sears warranty and had no B&S warranty to begin with in order to save B&S a PR nightmare.

As recently as 6 months ago there were still doing it... at least in the case of my neighbor.

Although Sears does negotiate with their L&G rider OEM (Husqvarna OP and MTD and now I guess Simplicity/Briggs) for engine prices without manufacturer warranties the engine manufacturer's generic lit I've seen in the packet accompanying new Sears L&Gs infers that the engines are covered under the manufacturer warranty and I've always wondered about that.

Smoke Color...

Light blue or grey....not black or brown.

The most smoking occurs at high rpm under load, but there is always a decent puff of the same color smoke at startup.

Mike

Walt2002.....concerning the pvc valve or breather. I assume you mean the one mounted under the flywheel on the front of the block. I removed the breather and the 'steel wool' like filter below it. Cleaned the filter, but not too dirty.
The breather seemed to work OK. I could suck air toward carb but not blow air toward crankcase. Also took breather apart and cleaned. Smoking did not seem to change any.

Mike

I don't know why it didn't smack me in the face earlier on!
Your symptoms can also indicate a leaking cylinder head gasket.
What can (does) happen is that a head gasket begins losing a small volume of compression from the combustion chamber into the valve pushrod gallery. This leakage of compression/combustion increases the flow of crankcase gases and oil mist out through the crankcase breather to be recycled back into the combustion chamber once again.
It only takes one leaking gasket to cause this to happen because the pushrod galleries of each head flow to the common crankcase.
The oil content in the venting gases can also raise the compression test readings you are seeing (and effectively mask the slight loss of pressure at the leak) in a couple of subtle ways. #1, oil being a liquid, can't be compressed so it actually reduces the confining space of the combustion chamber resulting in a higher compression pressure reading (than would be expected normally). #2, the oil content in the induction air "wets" the piston rings causing them the seal tighter (and sooner) than they would if they were operating under normal conditions.
Often you can actually see the leakage of compression/combustion gases out of the combustion chamber and into the pushrod gallery by removing the valve cover and shining a bright light into the pushrod gallery while the engine is running. Beware......the rocker arms will fling drops of oil at you so wear eye protection when doing this test procedure. The leak will produce distinct "puffs" on each compression/power stroke.
A "cylinder leakdown test" (requires compressed air source) can also be used to detect a defective head gasket.

Mownie,

Thanks for the suggestions....

I cannot run the test you suggested: "....see the leakage of compression/combustion gases out of the combustion chamber and into the pushrod gallery by removing the valve cover and shining a bright light into the pushrod gallery while the engine is running. ", because on the 26hp Intek engine the fuel pump is powered by a vac line from the valve cover to the fuel pump. No valve cover...no fuel!

I will have a leak tester tomorrow and see what that shows.

Mike

The engine will run long enough on the quantity of fuel in the float bowl to perform the test. You just gotta get the engine warmed up first, then you pop the valve cover and run the engine while watching for the puffs in the gallery.
Good luck.

Leak-Down test:

I just completed the leak-down tests with the following results:

#2 Cyl has 7% leakage. I understand this to be good.

#1 Cyl has 70% leakage! This does not seem too good! The air seems to be leaking, as far as I can tell, out the muffler. I do not see or detect any leakage in the pushrod gallery. I repeated this test a few times with the same result.

Before I tear anything apart I would like to understand, if possible, what this indicates, in conjunction with my running symptoms.

The running symptom is that the engine runs great and has normal full power. After mowing for about 10 minutes (full hot), it starts to emit blue smoke heavily.

The leak-down test seems to indicate that I have a leaking exhaust valve on the #1 cylinder. How could the engine run that well with that much leakage?

Some of you have indicated that I likely have a blown head gasket. Could a blown head gasket cause a combustion chamber leak that vents to the muffler when I do the leak-down test? If so, how? What would be the path of the leak?

Thanks for your help,

Mike

Did you have a means to "lock" or hold the crankshaft stationary with the piston of the cylinder being tested at TDC on its compression stroke?
Each cylinder must be set to its own TDC, compression stroke and the crank held stationary before applying air to the cylinder. I suspect that you did not have the cylinder (with 70% leakage) set to TDC, compression stroke when you did the test. This much leakage out the exhaust would indicate a defect in the exhaust valve and/or valve seat of that cylinder..........but that much leakage would certainly result in the affected cylinder being "dead".

Mownie,

I did not 'lock' the crankshaft but I did look at it to be sure it did not move when I connected the air. I know what you refer to because on the 'good' cylinder, when I connected the air supply, the crankshaft did rotate a couple of times until I got it exactly balanced at TDC. I never had this crankshaft rotation problem on the 'bad' cylinder because there was so much leakage there was never enough pressure to move the crankshaft! But, just to be sure that the exhaust valve was not being held open I removed it's rocker arm. Same 70% leak.

If, indeed, that much leakage would result in the cylinder being "dead" then why does the engine run so nicely (before it starts to smoke after getting hot)?

Mike

Mike,

Take of your engineer hat off, put it on the table, and back away...

Concern yourself with the how and less with the why.

When you have stumbled upon the cause then the remedy and the why will become obvious.

Some V configured engines or boxer engines (opposed twins) will seem to run well on just one cylinder, and even sound the same (until you get them into a very heavy load situation).
Something is "amiss" here because a leakdown test should be practically a carbon copy of the compression test results.
In your OP you state "Measured compression...both cylinders about 130psi". Realistically speaking, a leakdown test is often used to peg the culprit component AFTER a compression test discloses a deficit of compression in a cylinder.
The fact that you isolated the valve from its rocker arm would remove any influence that a compression release device might have on the valve (though I think the decompressor is on the intake valve cam lobe in this series engine, so an ACR shouldn't matter either).
At this point I believe it is rational to presume that the cylinder with 70% leakage has a defect in the head affecting the exhaust valve. Inteks have been known to turn loose of a valve seat (sometimes with catastrophic progressive damage), but typically that happens after an overheating event caused by rodent activity in the cooling fan shrouds.
Perhaps the exhaust valve seat of the cylinder is loosening and right now is "tilted enough" to produce the results you are getting with the leakdown test, but in use (after warming) the seat is being returned to its rightful position.
It would be a fluke for the valve and seat to have been "normal at the time you did the initial compression test, but I have not experienced everything the world has to offer either.
I think it might be a good idea to remove that head for a close visual inspection of the combustion chamber of the head.
Pictures of what the CC look like would be welcome.

justalurker and mownie,

OK, I'm convinced...time to "remove that head for a close visual inspection."

I will post pictures of what I find.

Thanks,

Mike

Ok guys...I finally dismantled my Briggs 26 hp Intek V-Twin.
Just to review...the problem I am having is a large amount of blue smoke at full throttle/load, after the mower had fully warmed up (hot).
Also, a leak-down test show a 70% leakage on Cylinder #1. Air could be heard coming out the muffler.
I have seven pictures to share with you...descriptions will be just before each picture. My 'conclusions' and/or further questions follow the pictures.

1. Cylinder #1 Head:
   Exhaust valve had been cleaned up on wire wheel before this picture was taken.

{{gwi:313984}}

2. Exhaust Valve:
After cleaning valve on wire wheel. In this picture you can see the only defect I can spot. There is a very slight bump or raised point at about 4 o'clock on the valve. This may have been holding the valve open enough to cause the 70% leakage.

{{gwi:313985}}

3. Cylinder #1 Block view:
Bore is clean/smooth with no scrapes. There is a 'discoloration' on one side but it does not seem to have any depth.

{{gwi:313987}}

4. Head Gasket - Head Side:
Seems to be perfectly intact. Certainly not 'blown out' as I have seen on a car engine. There is a very slight discoloration between the cylinder and pushrod gallery.

{{gwi:313988}}

5. Head Gasket - Block Side:
Seems also to be perfectly intact. In this shot you can see the discoloration a little better.

{{gwi:313989}}

6. Head Bolts resting in head (backwards):
Note that they are a nice gold anodized color, except for the one that was between the intake and exhaust pushrod galleries! It is black!

{{gwi:313990}}

7. Head Bolts:
Another view to compare head bolts. Note that the black one also has an area near the head that is discolored. It looks like it was blasted with something!

{{gwi:313992}}

....End of pictures
Questions:
Does the blackened bolt and very slight graying of the head gasket indicate a leakage that is enough to cause the kind of smoking that Mownie (see his previous post) talks about? Mownie says that a head gasket leak into the pushrod gallery would vaporize oil and that it would be transported to the crankcase, then to carburetor to be burned.
Is there anything that small engine users put on head gaskets to help seal better?
Some torque specs I have seen for this engine show 220 inch pounds for the head bolts. Does this sound correct? I don't have an inch-lb torque wrench. Is there any problem using a ft-lb torque wrench set at 220/12 Ft-lbs?
Does anyone know the torque sequence for this head?
Thanks,
Mike

We didn't get to see the most important pictures... the ones before you cleaned everything up and destroyed all the evidence. Don't you watch CSI?

Mike, I'm not wanting to pi$$ you off, but the farther you go into this the one thing that I want to scream is...

CAUTION... engineer at work
The more you do the more difficult you make it for us to help you.

Since you want us to read your mind and don't give us the info we need...

1. A mighty tiny piece of carbon is sufficient to hold a valve open.

2. The blackened bolt is a clue.

3. I coat head gaskets with white grease and use Bel-Ray 6in1 on the head bolt threads so they torque smooth.

4. The torque specs are the specs and whatever tool you use to apply the correct torque is acceptable.

5. Absent a specified torque sequence for the heads bolts a crisscross sequence achieves the desired result.

Would have been helpful to see in the intake and exhaust ports to look at the valve guides before cleanup and dis assembly.

I'll just bow out and wait to see how this story ends.

justalurker,

You wrote:

"I'll just bow out...."

I guess that will be fine with me...you obviously don't want to help...since you only to spew out criticism.

I did not come to this forum as an expert. I am just asking for help from those who can possibly shed some light on my situation.

For those of you that can supply helpful advice, I would be grateful.

Mike

Most come for help, listen, and then say thank you rather than argue at every suggestion.

Few have the arrogance to email privately and then insult openly on the forum. You are the customer that I show the door and point to the shop down the street cause you'll never be satisfied.

I don't suffer fools well and that's just one of my many failings, but if you take the time to review this thread you'll be surprised at how much good FREE advice you've been given and how reluctant you've been to take it.

There's nothing quite like taking the time to help someone using one's hard learned knowledge and experience and then being insulted when doing it or facing the demand that you've not done enough either on this forum or in the many private emails we've traded.

To bring this down to the level of a petulance that you've chosen I can only say... my tractor runs great, yours?

My apologies to the others on the forum but Mama always told me that when you've had enough to just say when.

Well I expect Mownie will be along with some expert advice soon. I have never heard/seen him saw anyone off at the knees though I have him sometimes.

In the mean time, you should be able to down load a free Service Manual at - http://www.mymowerparts.com/pdf/

As for blackened head bolts, most B&S head bolts around the exhaust valve are discolored compared to others, heat you know. I don't see any evidence of head gasket leakage in pictures. Often the leakage may just look like a pencil mark across the gasket.

That exhaust valve certainly has problems. I would still check the crankcase breather, that it is working freely and sealing. I alternately suck and blow on rubber hose coming from them. They should suck eaily, be considerably restricted blowing with a quick change over.

Hang in there.

Walt Conner

You may just find that once the exhaust valve is remedied and the engine is resealed that all is normal. You could try cleaning the valve and seat and see what you've got, though I wouldn't be surprised if a new valve was needed. lap them in with compound and clean them up good. How does thatseat look? Twins do strange things when 1 cylinder has a valve issue. Obviously, a non sealed combustion chamber isn't too efficient. Briggs head gaskets go in with the surfaces clean and dry with a touch of oil or anti-sieze on the threads. This would be a better forum for people to gravitate to if people could keep all the communication on the board and condescending remarks to themselves.

Well, the very slightly discolored area of the head gasket certainly "looks like" it could indicate some leakage.
The blackened head bolt looks like it has been exposed to combustion gases, can't think of any other way to get that hue without hot, sooty exhaust gases (combustion gases and exhaust gases are essentially one and the same, one is a millisecond older than the other).
The whitish marking near the heat of the bolt sorta, kinda looks like it was influenced by moisture (which is present in exhaust gases).
The exhaust valve shows ample evidence that it was doing a poor job of sealing.
I would like to see a photo of the valve seat (minus the valve).
If the seat looks as bad as the valve, I'd suggest a new valve and have the seat cut to a new surface (automotive machine shop type of job).

And just to clear the air about HOW a leaking head gasket into the pushrod gallery causes smoking and/or increased oil consumption.
It's because the volume of combustion or compression gases that leak into the gallery will then need someplace else to go or every gasket and seal in the engine would get turned inside out by the pressure build-up in the crankcase.
The leaked gases will vent out through the crankcase breather and then they will go right back into the cylinders again. Because the volume of gases now far exceed the normal "pulses" of crankcase pressure from descending pistons and normal blow-by gases, more oil droplets than the oil separator media of the breather can handle will arrive at the breather and so some of the oil will pass through the breather along with the extra gases, and it too will end up back in the combustion chamber.

Thanks for the suggestions....

walt2002...

I checked "http://www.mymowerparts.com/pdf/ " and can only locate Briggs Parts manuals there. They don't seem to have any Briggs Service Manuals listed....I have also searched via Google without success. My engine number is 446777-0244.
Crankcase breather - Before disassembly of the engine, I did inspect this. The 'steel wool like' filter was crankcase oil soaked and the breather looked fine. I could 'suck but not blow' through it. Still unconvinced, I opened the breather and it was clean inside.

tomplum:

The seat for the exhaust valve looks perfect. The valave has that 'slight bump' in the contact area and the valve has a pitted look all the way around the contact surface. I am in the process of lapping the exhaust valve. The 'slight bump' is gone and the rest seems to be cleaning up fine.

mownie,

I agree with your blackened head bolt theory. It seems that any leaking gasses would heat the bolt, but also find an 'escape route' up along the unthreaded portion of the bolt and out under the bolthead into the lifter gallery. This would carry any moisture with the gasses through the area that looks slightly rusty.

Mownie wrote:

"The blackened head bolt looks like it has been exposed to combustion gases, can't think of any other way to get that hue without hot, sooty exhaust gases (combustion gases and exhaust gases are essentially one and the same, one is a millisecond older than the other)."

To get some more information I removed the head from the #2 Cylinder. The corresponding head bolt was NOT blackened like the one on cylinder #1. So, even though the head gasket on #1 'looked good', it was probably leaking into that bolt hole and then on to the pushrod gallery.

"To get some more information I removed the head from the #2 Cylinder. The corresponding head bolt was NOT blackened like the one on cylinder #1"

2. The blackened bolt is a clue (from previous post)

"So, even though the head gasket on #1 'looked good', it was probably leaking into that bolt hole and then on to the pushrod gallery"

We didn't get to see the most important pictures... the ones before you cleaned everything up and destroyed all the evidence. (from previous post)

"...you obviously don't want to help...since you only spew out criticism."

Criticism or the help you were looking for and refused to accept?

Briggs 446777-0244-E1

Status Update:

The engine is completely apart. I think I found the problem that was causing the oil consumption (burned about 1/2 quart of oil per 1/2 hour of mowing!).

The rings were totally worn out.

The first indication of how much the rings were worn came by checking the ring end-gap, per the Briggs manual. The top compression ring measured an end-gap of .150 in. The reject dimension specified by Briggs is .030 in.!

The width of the compression ring (measured horizontally) was .099 in. on the old compression ring. The same dimension measured on a new ring was .196 in. That made the old ring a total of .194 in. smaller, in diameter, than a new one. That sure seemed like a lot of wear!

The old oil control ring (measured horizontally) was .065 in. A new ring measured .091 in. Also, the raised portion of the oil rings were completely worn off the old rings.

The cylinder bores were not scared or worn significantly. The bores were well within spec. They cleaned up easily with a cylinder hone.

Finding that much wear to the piston rings almost shouts "dust leaking into induction system".
Also, if dust indeed is the culprit, you need to be sure and carefully inspect the valve stems and guides (especially the intake valve) for excessive wear to those components.

As bad as the news seems to be at present, you are making progress (having identified a condition promoting oil consumption).

But you have to try to determine if another condition (breach in induction system) led to the other condition (worn out rings).

I was not surprised to find this much ring wear on the engine. I got it from someone who did little or nothing to maintain it properly. For instance:

1. The engine was about 8 years old and still had the original oil filter!

2. The engine oil, when I got it, did not even register on the dip-stick. Obviously it was very dirty, black and 'watery'.

3. The intake system was missing both the air filter and cover for the air filter. The top of the carb was exposed.

I am actually surprised that it ran as well as it did (after I changed oil, added air filtration, and rebuilt the heads). It had plenty of power and ran the mower quite well. The copious smoke was its only problem. I fact, it did a great job of riding my neighborhood of mosquitos ;--]

***"The intake system was missing both the air filter and cover for the air filter. The top of the carb was exposed."***
Learning this, I too am surprised the engine lived long enough for you to acquire it.
Good luck!

Sounds like you have it almost fixed. Sounds like it was cheap or free. I hope so.

"Sounds like it was cheap or free."

Well, not quite:

PARTS:

2 sets of piston rings: $65
Engine Gasket set: $35
Cylinder Hone: $30
Oil and Filter: $15

LABOR:

'cheap or free'

:--]

$145 at "BG's DIY Garage" vs. $500+ at some shops.
I like the BG bottom line better!

Amen to that mownie...

And I forgot the last item on the 'Bill':

-----

PARTS:

2 sets of piston rings: $65
Engine Gasket set: $35
Cylinder Hone: $30
Oil and Filter: $15

LABOR:

'cheap or free'

EDUCATION: Priceless

-----