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Craftsman 17.5 hp lawn tractor

Posted by brotherdl GA (My Page) on
Fri, Apr 27, 12 at 10:19

Model Number 311707 E3 495735. Changed the connector on the carburetor then oil started coming up threw the breather . I replaced the breather cleaned the carburetor .Runs but smokes bad then dies. oil is not over fill but low now after coming up in the carburetor . Help


Follow-Up Postings:

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RE: Craftsman 17.5 hp lawn tractor

Me thinks you had best go back to square one and start over! I can't decipher just what or where the hose is supposed to be connected, but evidently not where you put it!I think you are pressurizing the crank-case of the engine, which then forces the oil pressure in instead of out, and then forces the oil back into the carburetor. Hard to tell, but, seek professional help, before you ruin a perfectly good engine! (hopefully still good at this point!)


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RE: Craftsman 17.5 hp lawn tractor

"Changed the connector on the carburetor"

What are you talking about?

Walt Conner


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RE: Craftsman 17.5 hp lawn tractor

Like Walt.......it's not really plain what you are referring to.
But this has many of the symptoms of gasoline having found its way into the crankcase lube oil, most likely due to a defective condition in the carburetor float valve components.
What can happen is this:
Gas leaks into the cylinder and past the piston to arrive in the crankcase. There it mixes with the lube oil.
The next time the engine is run...........as soon as the engine, and the oil.......begin heating up.......the gasoline in the oil begins to boil out.
The boiling or evaporating gasoline causes pressure inside the crankcase which must vent out through the crankcase breather and into the air filter housing where the escaping gas fumes and oil mist get fed directly into the air being sucked into the carburetor.
As the engine heats further the volume of escaping gasoline vapors can become so great that the mixture being fed to the engine combustion chamber is too rich in fuel and oil mist to support combustion, and the engine might just stop running.
Perhaps you can fill in some blank spaces about just what and why you were doing something to something somewhere on the carb and we can piece together a better idea of what to tell you.


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RE: Craftsman 17.5 hp lawn tractor

Well I have worked on mowers before I replaced a plastic connector with the brass piece that has to be press in. I didn't clean the carburetor the gas leaked pass the needle valve into the oil . Ok so from there I figured that out. Then I cleaned the carburetor drained the oil and replace it with clean 30 Hd. Ok started smoking white a little then a lot to the point you couldn't see. I replaced the breather. It still does the same thing . I know where the gas goes into the carburetor so that not it. I also read something about the valve not going in and out the same so I looked and there are doing what their suppose too.It even runs good doing this at least until it dies Help


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RE: Craftsman 17.5 hp lawn tractor

OK, so you know where the push rods go down into the engine?
So start the engine with the valve cover removed (it will spit oil on you) and watch down inside the push rod gallery and shine a flashlight down in there and watch for little puffs of pressure escaping from the head gasket into the push rod gallery.
You see any puffs your head gasket is leaking.


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RE: Craftsman 17.5 hp lawn tractor

I not sure what puffs look like . Are they like oil bubbles? Is their another way to check the head pressure? I could maybe get a rental tool from auto zone. I am not sure what to get that would work on a mower engine. I not sure what else it would be beside a head gasket . What your thoughts on the subject Walt? Thanks for the help


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RE: Craftsman 17.5 hp lawn tractor

I can't recall exactly where I got the image below, but the little red arrows point to where the bottom of a cylinder head meets the top of the cylinder block.
The head gasket is sandwiched between the head and the block.
The picture is not of a Briggs engine but will suffice to illustrate where the puffs of compression will be escaping from if a head gasket fails. The puffs will be blowing out sideways from the gasket seam and will be easily seen by shining a light in there.

Photobucket


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RE: Craftsman 17.5 hp lawn tractor

I think I understand .I going to have to take the springs and rocker arm out of the way to see the puffs. I will have to re adjust the valves .I'll need to know which is exhaust and Intake along with how many thousands to set them at. I appreciate the help . I need this mower ! Thanks for taking the time to help me out.


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RE: Craftsman 17.5 hp lawn tractor

How's it going to run without the rocker arms?

Just remove the valve cover.
Have a rag handy.
Start it up, quickly observe and shut it off.


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RE: Craftsman 17.5 hp lawn tractor

Exactly what bill said.
I might should have explained that the image I posted in no way implied that the rockers and springs or other stuff had to be removed to watch for the puffs.
I just used a handy "stock image" from photobucket to point out where the puffs would be coming from.
Now if I could have posted a video I guess that would have been better but I don't have one of that.


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RE: Craftsman 17.5 hp lawn tractor

It is a little difficult to see past the Push Rod Guide Block on this model engine.

Walt Conner


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RE: Craftsman 17.5 hp lawn tractor

Sorry I was just looking at the picture.I have not done anything yet. I thought it was just going to be bump over not running . I will start it up this weekend and check it out. I'll go from there. Remember I know a little about this .I'm not an expert just a novice. So be patient with me. Thanks again for your help


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RE: Craftsman 17.5 hp lawn tractor

I'm going to take the cover off this evening its about 100 degrees right now the temp. I had one last thought the oil is coming up threw the rubber hose that is attached to breather What if I replaced the breather with one with no hose like the one on my 19.5 it has a broken connecting rod anyway and is just junk setting around, I know that not the answer but I don't understand why a head gasket would make oil come out of the breather up into the carburetor. Anyway I will post tonight when I see what is happening . Thanks again for everyones help


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RE: Craftsman 17.5 hp lawn tractor

"but I don't understand why a head gasket would make oil come out of the breather up into the carburetor"

Because the combustion gases leaking past the head gasket pressurize the crankcase. It's more than the breather can handle.


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RE: Craftsman 17.5 hp lawn tractor

Ok that makes sense . I took the cover off and I could not see anything but oil mistying around the area you said to look at it look like smoke and of course oil in my face I believe its the head gasket is blow so bad its blowing out there. What do you think? Thanks for your help thus far.


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RE: Craftsman 17.5 hp lawn tractor

If the "mist" is PUFFING OUT every time that cylinder fires, that's your clue.

It's not what WE THINK. It's what YOU observe.


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RE: Craftsman 17.5 hp lawn tractor

That what's it doing thanks for your help. I have to get the gasket and find the head bolt specs.Then go from there.


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RE: Craftsman 17.5 hp lawn tractor

I have the gasket and i looked up the specs its 220 inch pounds on the head bolts. I am not sure how procedure goes. If y'all could direct me I can do this. Thanks for your help thus far.


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RE: Craftsman 17.5 hp lawn tractor

Download the IPL from the Briggs website for your engine.
It'll have an "exploded view" and proper part terminology.
311707 E3 is NOT correct. It'll be something like-
311707 ???? E3.

Look for "WALT" on the valve adjustment thread. He has a detailed procedure which is very good. It'll tell you things NOT to do, which can be even more important.....

220 inch lbs./12 equals 18.333 ft-lbs.

Don't get the pushrods mixed up.


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