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712 crank case pressurized?

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Hi guys been a while since I was here. I recently purchased a 712h that has sat awhile. Thing started right up but it seems to have pressure in the crank case, it pushes the dip stick out. So I put new rings in it and it still does it. Could it have a plugged breather? Any suggestions would be appreciated

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It could, maybe you should clean it. Hopefully you didn't slap a new set of rings in a old engine without micing it for wear, if you did it might not smoke and it might even run a little better, but it still might put pressure in the crankcase. See even if the cylinder looks smooth and slick it can be both tapered and out of round due to the way the piston goes up and down with the connecting rod. So lets say your cylinder was in super duper shape and only.05 out of tolerance and you put in a set of standard size rings in. It might help power and stop smoking, but with a enlarged cylinder and a tolerance in the rings of .005, on the upward stroke, lots of air could still get by the rings. Of course it could be your breather. Just curious, you put a set of rings in and didn't pull the breather cover?, Did you check the valves?. Crank wobble? See there a big difference between an engine rebuild and changing the oil or spark plug, lots of things like tolerances, and the many steps that go along with an internal engine rebuild. Checking the wear on the cylinder, crankshaft, and valves, boring a cylinder, replacing a sloppy or worn connecting rod, piston or wrist pin. All these things need checked with a micrometer for tolerances and wear. On aircraft they have major inspections and rebuilds by hours, and when an engine or airframe has so many hours on it, there are many things to do other than change the blades, tractors are the same, big one or little ones. Attention to detail will serve you well, because if you don't think you have time to do it right, wait till you have to do it twice, or cause it further damage. Good Luck. probably do have a dirty breather, but.....

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quote:Originally posted by haykarenhardy

I have a 712 that will push out the dip stick, My 301 is in good shape and uses little oil, could your rubber seal on the dip stick be the problem? Became hard due to age?Stan

id="quote">I doubt thats the problem, since if the crankcase ventilation is working properly it shouldn't push the dipstick out anyway, but since you brought it up, does anyone now what the crankcase pressure on a kohler single should be or is? good quesion

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With a good engine and a good working breather the crankcase should be neutral or even be a little negative. One way to check for excessive blow by is to take out the dip stick or oil fill cap and put a rubber glove over the opening. A bad engine or bad breather will blow up the glove, the opposite on a good engine and breather.

The breather valve (reed valve) lets out excess crankcase pressure and closes when it is neutral to atmosphere or a negative to atmosphere.

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