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I have a 2013 D-105 lawn tractor with 110 hours on it. I maintain it properly per the owner's manual and until this season it has never used a drop of oil. Now I am adding a bit every week and I occasionally get a puff of white smoke. I checked compression and its reading right on 100 psi. The plug was also oil soaked. Am I likely to have bad rings or a scored cylinder already?
 

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You have a different engine than my D160 has but...

Go ahead and check compression. I don't know that it would be "likely" that you have a cylinder or ring issue but it is possible.

If your compression is good, check your valve lash adjustment. The Operator's manual says to do that service at 200 hrs but my machine was losing oil and I found that one valve was well out of specs and I only had 80 hrs on it at that point. Once adjusted it runs much better and oil consumption went away.
 

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I have a 2013 D-105 lawn tractor with 110 hours on it. I maintain it properly per the owner's manual and until this season it has never used a drop of oil. Now I am adding a bit every week and I occasionally get a puff of white smoke. I am going to take a compression reading but I am not sure what the proper compression range should be. Am I likely to have bad rings or a scored cylinder already?
Your D105 has the infamous B&S 17.5HP engine. My brother's LA105 just did something very similar and it ended up being a blown head gasket, which is something these engines are famous for.

It is certainly possible that you could have worn rings but it would be unusual given the low hours and that you maintain it properly. One other thing that can cause white smoke and oil consumption is a blocked crankcase vent. It is a reed valve assy located on top of the engine and has a small rubber hose attached to the intake manifold.

The new head gasket was only around $20 and it was very easy to replace. If you have the ability you might want to just go ahead and pop the head and have a look-see. That way you can check the head gasket and see what the cylinder walls looks like. When we replaced the head gasket we got a kit from Amazon that included a head gasket, exhaust manifold gasket and intake valve rubber seal. The valve cover just uses rubber silicon sealant. It's also a good opportunity to check and adjust the valve clearance.
 

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You have a different engine than my D160 has but...

Go ahead and check compression. I don't know that it would be "likely" that you have a cylinder or ring issue but it is possible.

If your compression is good, check your valve lash adjustment. The Operator's manual says to do that service at 200 hrs but my machine was losing oil and I found that one valve was well out of specs and I only had 80 hrs on it at that point. Once adjusted it runs much better and oil consumption went away.
Not sure how valve lash can effect oil consumption. If the clearance on the intake valve is too great it can cause issues with the compression release which results in hard starting or failure to turn over. But normally the only valve related issue that will cause oil consumption is a leaky valve guide or rubber seal... or if the valves were too tight and got burnt to the point that it no longer seals properly. But these issues are typically not remedied by an adjustment.
 

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Discussion Starter #5
You have a different engine than my D160 has but...

Go ahead and check compression. I don't know that it would be "likely" that you have a cylinder or ring issue but it is possible.

If your compression is good, check your valve lash adjustment. The Operator's manual says to do that service at 200 hrs but my machine was losing oil and I found that one valve was well out of specs and I only had 80 hrs on it at that point. Once adjusted it runs much better and oil consumption went away.
Compression reads right at 100 psi. Not sure if that is good or not but I would think so......
 

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Not familiar with the B&S 17.5HP, so I'll just throw this out there. Check the crankcase breather. It hay have a reed valve that's stuck or a filter that's clogged...or a mud wasp nest in the discharge tube!

Another long shot is the fuel pump. Is this connected in any way to the crankcase? You may(??) have a cracked diaphragm and be actually pumping oil into the fuel...although this should give you a constant light blue exhaust. Bob
 

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Not sure how valve lash can effect oil consumption. If the clearance on the intake valve is too great it can cause issues with the compression release which results in hard starting or failure to turn over. But normally the only valve related issue that will cause oil consumption is a leaky valve guide or rubber seal... or if the valves were too tight and got burnt to the point that it no longer seals properly. But these issues are typically not remedied by an adjustment.
I'm still trying to figure out exactly what was going in but the valve that was out of adjustment just happened to be on the side where the vacuum line is for the fuel pump. Oil was getting blown up into the vacuum line and fuel pump so somehow the valve lash being out of adjustment appears to have created a pressure issue within the valve cover.

Each time I'd shut the machine down for any period of time the oil in the fuel pump would seep from the vacuum side to the fuel side so when I'd start it again, I'd get a blast of blue/white smoke when it started.

Once I adjusted the valve lash that all went away. I bought a replacement fuel pump in case that was the culprit but haven't put it on yet.
 
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