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Discussion Starter · #1 ·
I saw white smoke blowing out of the breather cover vent hole, so I took breather cover off down to reed and left the inside cover on, I turned the engine over with the inside plate still on and as soon as it started turning over there was oil comming out from the little bottom hole on the inside breather plate. Why is oil comming out from the breather plate?? The fuel pump, bottom of outside breather plate and all along the engine below the breather plate is covered in oil / dust. Is oil getting past the piston and then down into the valves and valve guides? What is my next step, I did rebuild the engine last summer but did not have it bored to 1 over. I know what the answer is (take engine out and redo it again) but I was hoping to delay as long as I can. Any help greatly apreciated.
 

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I have just tore down my 14hp and found oil in the breather of mine. There was a thin layer of silicone around the plate so none came out of the side. So I am also interested in the answer to this question. Is oil suppopsed to be in the breather palte area? Or is it a condition of blowing blue smoke when it ran?
 

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coalcracker said:
I saw white smoke blowing out of the breather cover vent hole, so I took breather cover off down to reed and left the inside cover on, I turned the engine over with the inside plate still on and as soon as it started turning over there was oil comming out from the little bottom hole on the inside breather plate. Why is oil comming out from the breather plate?? The fuel pump, bottom of outside breather plate and all along the engine below the breather plate is covered in oil / dust. Is oil getting past the piston and then down into the valves and valve guides? What is my next step, I did rebuild the engine last summer but did not have it bored to 1 over. I know what the answer is (take engine out and redo it again) but I was hoping to delay as long as I can. Any help greatly apreciated.
When engines have many hours of use, the cylinder bores exhibit wear and that wear is often not uniform. The bore can go slightly oval and it can often have a taper to it with the bottom of the cylinder measuring larger than the top. Boring the cylinder back to a perfect and uniform circle from top to bottom is the only way to remove "blow-by", which is the term used to describe what happens when the rings are unable to seal against the cylinder walls properly. It's those hot, gasses blowing by the rings that enter the crankcase where all that oil mist created by the "dipper" on the end of the con-rod is floating around. The crankcase breather is there to allow excess pressures to vent outside of the block but to also capture the oil from the mist that is attempting to escape the block. That's why there is a steel wool type of filter in that breather.

But if the blow-by is substantial, the breather is overcome with the amount of oil mist it must deal with. Also, a damaged, broken, worn out or improperly installed reed valve will contribute to the problem. If you did not have your cylinder bore measured by a competent machinist that is familiar with engine rebuilding, then conducting a true rebuild of the engine is your only solution. The only way to determine what's going on inside your engine at this point is to do a "leakdown test". You need to find someone who can do this for you or will loan you the tester and instruct you how it is performed. The leakdown test will quickly demonstrate if the combustion chamber is capable of holding pressure or if that pressure is leaking down past the piston rings or the valve/s or both.
 

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If the breater screen/material is what you are referring to I'd take a look elswhere on this site to find somethiing else to use or call a local dealer or NAPA store and get a new one. There is a thread somewhere on here that discusses this exact issue. Cant recall where but might be in FAQ's or 'Where to Buy Stuff' or maybe even another thread right here.
 

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Discussion Starter · #10 ·
Hydriv - Thanks for explanation, I had a feeling that it was blowing past the piston and rings. When I took off the breather plate, the steel wool filter was saturated in oil. I did a pressure check and had 120 on the gauge. What is the pressure range I need to be at?? Next I did leak down, I am almost 100% certain I had it a top dead center, and I could hear the air coming out of the muffler. If I hear air coming out of the exhaust then it has to be letting oil down the exhaust valve..correct?? If thats the case then the valve is not fully seated, right, or can the valve guide have to much space between valve and guide?? If I get the cylinder bored out by machine shop that should stop the blow by of oil???
 

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coalcracker said:
Hydriv - Thanks for explanation, I had a feeling that it was blowing past the piston and rings. When I took off the breather plate, the steel wool filter was saturated in oil. I did a pressure check and had 120 on the gauge. What is the pressure range I need to be at?? Next I did leak down, I am almost 100% certain I had it a top dead center, and I could hear the air coming out of the muffler. If I hear air coming out of the exhaust then it has to be letting oil down the exhaust valve..correct?? If thats the case then the valve is not fully seated, right, or can the valve guide have to much space between valve and guide?? If I get the cylinder bored out by machine shop that should stop the blow by of oil???
Why not do a valve adjustment first and then try the leakdown test a second time?

And if you get the same results, how about pulling the head and remove all the carbon build-up from the piston, head and valves? Inspect the valve seats and valves carefully for burning or cracking. In other words, let's not leap to any conclusions until you have checked other possibilities.

If it turns out that the engine needs to be bored, then the machine shop needs to inspect the valves, valve seats and valve guides so that a complete overhaul is performed that will remove all of the leakage. Realistically, a valve must be open for compressed gasses to get past a valve seat. If you are telling me that you conducted a compression test and got 120 PSI, then that is very good. Anything over 100 is very acceptable. Anything under 85/90 indicates problems.
 

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Discussion Starter · #14 ·
Gentleman - thanks for the help - Ok so if 120 PSi is good then it has to be improper breather assmebly, (which I just reassembled the breather last night), or worn valve stems / guides?? I will try to clean head later on in the next few weeks, and get a feeler gauge in there for the valve to tappet clearence to make sure I have the correct clearance. I should have .17 to .19 on the valve to tappet clearance???? correct?? Either way I have alot of air blowing out of the breather area and the engine is using an essive amout of oil right now.
 

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Dont forget the amount of air which comes out of the breather may seem excessive when it really isnt. This is a single cylinder engine and when the piston travels from TDC to BDC its pushing a lot of air.
 
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