Briggs Intek 20HP Using Oil

[Mr. Shamrock]

Hello, I just joined today after searching for an answer to what seems like an impossible question. I have a 2007 Snapper 250Z with a Briggs 20HP Intek V-Twin. I bought the mower new and have handled all the maintenance myself. I am a long time motorcycle tech so I know my way around an engine. This has me boggled though - During the last season my mower has began to use just under a quart of oil during each and every cut (roughly 2 1/2 acres). Here's the kicker - it doesn't smoke or leak. To use that amount of oil I should be able to spray for mosquitoes as a side job. I was running a Wix filter and some non-Briggs oil and even though I had my doubts I went back to all Briggs parts and it still does it. I removed the engine breather and noticed the oil collector was completely saturated and the reed valve in there was stuck open about 1/16th of an inch. I wasn't sure if this was normal (it didn't seem right) so I ordered a new valve and oil collector. I also noticed when I had the intake off that there was A LOT of carbon build-up on the valves - especially the left cylinder. This cylinder was lower in compression than the right one - Left:95 Right:120. Obviously this isn't good so while I was waiting for the new parts to come in I did a seafoam soak in the intake runner. I got all the parts in today and checked compression again - Left 115 Right:125. Better but still further apart than I like to see. So since I did not remove the head I figured I would run a good dose of Seafoam in the gas and go run the mower to mulch up all the fallen leaves in my yard. I ran it for a good 2 hours and immediately checked the oil level and then drained it. It came out BLACK, so the Seafoam was doing its job, but the level was still down a bit. Not quite as much as before but right at the bottom of the hatch marks on the stick. While it was still warm I put the filter back on, reinstalled the drain plug, and put 2 quarts of mineral spirits in it and let it sit for about 15 minutes. I then drained it out - it came out dirty at first, but cleared up. I then ran a quart of oil through it just to see how it came out. It drained crystal clear. This is where I am at this point. I am going to get a new filter, oil, and spark plugs tomorrow and hope for the best. Oh also the spark plugs were BLACK with carbon so I cleaned them before running the mower today and when I was done they were dirty again - not as bad, but not right.
I think I am on the right track, but this has me scratching my head. I have changed the oil religiously (twice a season) since it was new. I adjust the valves, replace the air filter and prefilter, replace the plugs, and replace the fuel filter every year. Way sooner than it calls for, but the parts are cheap so why not. How can an engine be using this much oil and not smoke or leak - Any idea's??????

 

[reddragon]

wow!.....i think you have a factory defect engine.....i would think you would see more smoke...but ive had sneaky oil burning cars before......i dont like additives and dont use them except in desparation.....ive had satisfactory results from LUCAS oil treatment...beware[ its thick stuff!]

 

[Mr. Shamrock]

Thanks for the reply. I know it seems like an impossibility, but it doesn't smoke (besides the normal little puff at start-up due to choke being on). If I hadn't been witnessing it for the last season I wouldn't believe it. One thing I have considered is - Is it possible that somehow the recommended amount of oil is too much? It calls for 64 ounces according to the manual. I am relating it to my motorcycle knowledge and one of the bikes that I know of that is prone to carbon build-up is usually due to overfilling the oil because the dip stick isn't really accurate.
Also is it normal on these engines for it to take a long time for the oil to drain. My snapper has the convenient hose with the plug in it and even with the motor hot it doesn't come out real strong - it isn't dripping, but just has a tiny stream. It takes about 15 minutes for all the oil to come out.

 

[ILENGINE]

The next steps to your engine at least from a dealer standpoint would be a leakdown test and a crankcase vacuum test. The leakdown to check for any excessive leaks past the head gasket, valves, rings. the crankcase vacuum test to check for air leaks preventing it from maintaining proper vacuum.

 

[Sammy the Red]

I let my oil drain for about 1/2 hour.
Always seems like it takes forever.

What weight and brand of oil have you been using ?
What weight and brand did you use before ?

 

[Mr. Shamrock]

I let my oil drain for about 1/2 hour.
Always seems like it takes forever.

What weight and brand of oil have you been using ?
What weight and brand did you use before ?

Ok so my drain time is normal then.

I have used either SAE30 or 10W30. It was always changed with SAE30, but a couple times when it was low I topped it with 10W30 b/c it was all I had. It has either been Briggs oil or whatever brand O'reilly sells for mowers. There were 2 oil changes that I recall when I didn't go get Briggs parts and ended up at O'reilly's getting a Wix filter and whatever off brand oil they have for mowers.

 

[RobertBrown]

The next steps to your engine at least from a dealer standpoint would be a leakdown test and a crankcase vacuum test. The leakdown to check for any excessive leaks past the head gasket, valves, rings. the crankcase vacuum test to check for air leaks preventing it from maintaining proper vacuum.

Hey Ilengine
Could it be migrating to the transmission somehow?

 

[reynoldston]

115 and 125 compression I would say is normal compression, only 10lbs different is good. You will find that on any normal engine. You say it is using oil and not smoking, I have also seen that. For using oil the first thing I would check would be the intake valve guides.

 

[Mr. Shamrock]

115 and 125 compression I would say is normal compression, only 10lbs different is good. You will find that on any normal engine. You say it is using oil and not smoking, I have also seen that. For using oil the first thing I would check would be the intake valve guides.

You might be on to something. When looking down the into the head I could see there was a huge amount of carbon around the intake valve. I assume it was causing the valve to not close all the way and that was the reason for the first 90 PSI reading. After soaking in Seafoam for a few days it jumped to 115. I read on another forum to pull the valve covers one at a time and start the mower and look for leaks. Supposedly the common head gasket failure spot will be evident with it running. For the record the engine runs great and there is no noticeable loss in power. If it wasn't for it using more oil than a 2 stroke I would never know there was an issue. For the life of me though I can't wrap my head around an oil loss with no smoke or leak! Where does it go?!?!?!

 

[reynoldston]

You will find it is a lot like a motorcycle or any engine yes it can burn oil and not smoke. Seeing you have a lot of carbon around the valves and not smoking I would still be checking the valve guides. When the intake opens you have vacuum around the valve head and if the guide is loose you are sucking oil down pass the loose guides. On cars or truck they have valve stem seals but I never came across that on mower engines but maybe there is such a thing?