Deere LA125 Briggs 331877-0113-B1

Initial symptoms: Would start and run fine for several minutes when cold. Eventually would start smoking blue smoke under load then surge and eventually die. Adding choke would prolong dieing. The oil, while not over full, smelled of gas, and signs of oil at the fuel pump. Changed oil and filter which eliminated the smoking, and changed the fuel pump, but still dies after a time. Dropped the bowl on the carb and it is like new. Gravity fed fuel to it and it would run until I got bored holding the gravity tank (<15 mins) with blades engaged and no smoking.
The pulse line for the fuel pump comes off of the oil fill/dip stick tube. I pulled the line and it is half full of oil. Emptied the line and tried again and it ran longer, but eventually the same symptoms reappeared and the pulse line is again filled with oil.
This unit is only year and a half old. I haven't been into a breather reed on one of these...was wandering if anyone else has experienced issues with these engines or similar problem? It cranks and runs fine when it gets fuel and although I know the valve lash should be checked as well, just looking for any opinions or experience with this issue....still cold out there so limited time and long time customer also in hard times.

Preciate any insight/opinions

 

Hello Scott,

I haven't ran across this type situation as of yet, But it seems if it were a breather reed issue you would be getting excessive oil into the air filter assembly as well ?

Something I would check is as you mentioned the valve clearances, Pay attention to the exhaust. Also make sure the exhaust valve is opening fully compared to the intake. Also check that both valves are closed in relation to the piston at TDC comp. stroke, I'm thinking there may be a valve timing/lobe issue since this appears to be one of those press together camshafts looking at the parts break-down. Possibly the exhaust valve is closing a little too soon causing a little extra crankcase pressure which is blowing the oil back up into the hose.

Sorry I can't give you a exact answer, But maybe you'll find something with the few bones I threw your way.....

Good Luck !

 

Kinda what I was looking for Tech thanks as always, any bones are welcome as I am scratching my head over this one.

If the breather was plugged...how would the air filter get excess...?

 

This engine doesn't have a breather/filter per-sey, It has a reed plate like Kohler Commands etc.... If the reed were not seating or broke like Kohlers are known for doing the air filter assembly would be getting oil too most likely, That's why if there's no sign of oil, I myself would look into the cam/valves (under the valve cover) first before removing the flywheel....


Cya

 

sounds like the blown head gasket that occurs so often on that model of briggs

 

That crossed my mind too, but not too sure. Was waiting for further info.

 

Guess I have been too far since my theory, but, trying to think about how a head gasket would cause excess crankcase pressure (which I am thinking is what is causing the oil to be pumped up the pulse line) and or not show any other symptoms.
The air cleaner housing is also like new, dry as a bone and barely any dust or dirt. The thing seems to just want to run without any stumble or miss or anything, no belch when engaging the blades and barely even stumbles when doing so....as long as it gets fuel. With a gravity tank mounted it will mow 4" of soaking wet prairie grass without so much as a hiccup.

I got it nosed up into the stall and the hood off, but had to trek a few inches of snow to get to the shop, record lows tonight as well as record low daytime highs , and no efficient heating out there, but hope to get the valves checked tomorrow.

Thanks for chiming in, will keep it all in mind and keep you updated.

 

One other thing I seem to be foggy on....
This reed breather...anything like reed valves on motorcycles? My thinking is it should seal when the crank creates vacuum and release when under pressure....???

These problems only stay fun for so long , actually felt kinda good about even finding the problem...good to know I still got plenty to learn too, means I need to keep on going

 

Valves clearance:
Intake .004
Exhaust .006, adjusted to snug .004

After this I re inspected the breather tube to the air cleaner housing. This engine has an elbow (180 degrees) that goes from the air filter attachment point to the inlet of the carb. The breather tube connects at the bottom of this bend so not likely to contaminate the filter. I reached into the elbow with a finger and got some oily residue...so I pulled the shroud/fuel pump bracket/ elbow...and found the breather tube is indeed contaminated with white milky oil as if water contaminated. Also the reed/breather cover has oil and a pool of oil in a valley atop of the engine....
Looks as though the flywheel needs to come off to remove the breather/reed...
I am thinking I have found the culprit, but will wait until I hear back from you Pro's

Thx agin

 

Well Scott,

As you know we have to start somewhere when diagnosing issues, It's always best to start with the easy things first. Since the valves and cam check ok a cylinder leak-down test would show a partly blown (at the oil return area) head gasket, If that past the test then look into the breather reed. If you don't have a leak-down tester it would be less work to check the reed over removing the head so it's up to you which direction you want to take.....

 

So with a leak down test, assuming the rings are sealing then if the head gasket was leaking between the oil return area, then I would look for leakage from the oil fill tube...?

I don't have one but might be able to borrow or make one cheap enough, and I do need one anyway....

With the evidence of oil in the breather tube and reed cover...I am leaning that direction. Not sure it matters, I always seem to chose the wrong one regardless

 

That's correct, There will be some leakage past the rings into the crankcase and out of the dipstick tube. That's where the gauge on the leakdown tester comes into play, If there's over 15% leakage there is a problem with the gasket or rings. There should be little to no leakage out of the carb or muffler if both valves are seating correctly.

This looks like a decent price for one made in the good ole US of A; Amazon.com: Star (STACLT-2PB) Cylinder Leakage Tester: Automotive

Cya

 

Well it's not the breather....
So I am still batting 1000
Might be able to get the head of tomorrow....

 

Finally got the head pulled on this thing. Really hard to tell for sure but since the gasket is totally in at least 3 pieces now, (middle came off fine but flaking on both the engine and head left) I would say it's a good bet and now has to be replaced anyway.
Ordered but unknown when it will be in....when ever next order is full to save shipping...

 

Got the head gasket replaced, seems to have been the problem.

Man are these engines getting "chincy" specially the air breather/shroud/housings mounts etc......

 

Cool... glad you got it. I have one with excessive crankcase pressure that I'm messing with now. A leakdown test has air pouring out the crankcase. I figure for sure the head gasket was blown. I remove it and it's not. I looked at the top compression ring gap.. looks like .015-.020"... and no funny marks on the cylinder wall to indicate wide ring gaps or broken rings, so I put it back together with a new head gasket. It still blows has way too much crankcase pressure. I checked the PCV as well with no results. I guess I'm gonna have to pull the piston out.

 

Weird one cheese,
Wouldn't leak down show a ring with both valves closed?

Had another issue arise on mine as well, seems it will continue to run now, but I did notice the muffler start glowing....ran fine for the first test of 15m mins. Went to pull it back in the bay to pull the blades, sharpen then install and run again and it started running a bit rough and backfiring...
It was pretty chilly when I adjusted the valves so hoping that is all, or maybe a pushrod was not quite seated or sumin....

 

Yep, check the valves again or it could be running lean.

 

Valves checked right on.
Changed out the intake gasket since it had swollen and would not go back in the groove on the plastic intake.
Same thing, pull the flywheel cover and I be
Flywheel collar has broken...key only partially sheared (barely a mark)

Torque spec I find is 145ft/lbs....

Anyone have a different number...???

 

145 should be fine as long as there is no grease, oil, or dirt on the mating surfaces. I use an impact and just tighten it good. Never a problem.

 

Well that is what I did too cheese, same impact and setting that removed it.....

Just hate it when that happens on my watch....