My B&S engine is guzzling oil

I have an Ariens riding mower model 936042-00 powered by an B&S engine 406777-0442-B1. It has always been well maintained but gets a good work out. It mowes about 2.5 acres each cut. Last year all of a sudden it started to use excessive oil. By now it's about a half a quart to do those 2.5 acres. There is no excessive smoke coming from the exhaust or burnt oil smell in the air, there are no oil leaks or drippings on the floor. But both spark plugs barely make it through the mowing session, By the end of the 2.5 acres they are pretty much fouled up to the point were the engine starts having difficulty running. When I pull the plugs they are a mess, they are black and totally cloaked up with oily crud and sod. So I clean them and put them back and everything is fine for another mowing. Engine runs great without missing a beat. I checked the compression and it was a 130 on both cylinders. Does anybody have a clue what could be the problem with my engine?

I am absolutely surprised by the lack of responses or comments on this forum. I always considered this forum the premiere number one source of knowledge when it comes to everything "small engines" but apparently I am wrong. I am sure that my engine problem is not something isolated or unusual but a rather common occurrence as engines rake up hours. 36 views and nobody has a clue what it could be. Well, I guess I have to dig into it and find out myself.

Thank you SRT. Here is what I did so far. I removed the heads and I found both head gaskets to be in good shape. Also the valve stem seals seem to be tight and snug and the valves themselves virtually have no excessive play in their guides. The top of the heads are black with caked on soot and somewhat lesser are the tops of the pistons. (See pictures) If there was a problem with the piston rings would I still have that good a compression on either cylinder 130 +/- 2? Do you think I should put the heads back on and do a leak down test? Would that tell me more? Thanks Rick

This site is acting crazy.
 
On my "alerts" for new posts, it shows (copied below) your response but NONE on this site...
 
Quote:
 
Thank you SRT. Here is what I did so far. I removed the heads and I found both head gaskets to be in good shape. Also the valve stem seals seem to be tight and snug and the valves themselves virtually have no excessive play in their guides. If there was a problem with the piston rings would I still have that good a compression on either cylinder 130 +/- 2? Do you think I should put the heads back on and do a leak down test? Would that tell me more? Thanks Rick
 
End quote.
 
A leak down test would show how well the rings, valves, etc  are sealing, (of course).
I suspect their sealing just fine (compression shows us that), but does not tell us anything about the 
oil rings.  
 
You've done / checked about everything on the top end and ruled that out.
 
Besides the time to pull the engine, you'd only need a side cover gasket 
AFTER pulling the side cover, pistons and rings out.
 
I'd check that as your that deep and it really isn't much more to do
(as you seem to be fine with mechanicals)...
 
...

I removed the flywheel and now I can see that my idea of accessing the piston rods through the top is a no no. The top is all one piece. Looks like the engine needs to come out unless I can figure out a way to remove the sump from the crankcase by jacking up the mower. This is my story, always the worst case scenario. Oh well!

My own 18 HP Briggs going after a damaged piston (valve let loose)
 

 

 

 

OMG SRT, I guess that head is ruined. That exhaust valve sure did a number on you, yikes! Yours was a 1 cylinder engine looks like. Today I was able to download a great repair manual, with all the specs, torques and what not for my specific engine. Nothing can go wrong now. I am ready to go at it or bust - hahaha. I'll keep your posted. Thanks for the pics.

My machine all done (with the above mentioned engine, 2005 model):
 

 

 
 

Ok it doesn't show on this site but in my e-mail, you wrote:
 
Wednesday, May 15, 2024 6:28 PM
ueww40 just made a post in Briggs & Stratton Forum:
"Re: My B&S engine is guzzling oil"
Alright, I got it all apart, but to my dismay I still don't see anything wrong. None of the rings are broken, were stuck in the groove and the compression rings have a healthy gap of 3/8" and have a lot of spring. However, the oil rings are a different story. Compared to the upper 2 rings they seem collapsed without little or no spring to it. As you can see on the pictures the 2 outer rings barely have a gap of about 2 mm and the curly center rings has no gap at all. Is that normal or should they look more like the compression rings? The rings on both pistons looks just about the same.
 
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And make sure you CLICK on the  "OPEN FULL VERSION" at the top, or nothing will post..