Craftsman Riding Mower Leaking Gas Thru Exhaust

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  #1  
Old 08-21-13, 02:48 PM
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Craftsman Riding Mower Leaking Gas Thru Exhaust

Craftsman LT2000
Model 917.288031 or 917.28803 Have two books with different model #s.
500CC 17.5 HP
Briggs Stratton Intek

For over a year I have been jumping mower off with car.
Today engine would barely turn and never started. And when I say barely turned, I mean it did not really make a full round of turning that I could visually see from the top of the engine. Had filled the tank up with gas and it was leaking out the front of the mower thru the exhaust.

For the most part, since I found out, have been using 100% gas, no ethanol.

I took the little thing loose from under the carb bowl to see if that need was stuck and it appeared to be moving freely. Put it back in and tried again, same thing.

Had just changed the oil 2 months ago and does not appear to be any gas in the oil.

Thanks in advance for any advice or guidance.
 
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  #2  
Old 08-21-13, 03:50 PM
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If you have gas coming out the exhaust you probably have gas in the oil (will need changed). With that in mind you likely have a leaking float valve which precipitates all your problems. That's what you have to fix first.

Then purge the cylinder with the plug out to get the gas out (just spin it over a few times with the plug wire tied back to prevent arcing).

Then change the oil and start it up.
 
  #3  
Old 08-21-13, 05:46 PM
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Thanks!! How do I repair this leaking float valve?
 
  #4  
Old 08-21-13, 06:17 PM
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The easiest way is really to just replace the valve. That way you aren't messing with working on it, then assembling to see if it works.

The needle valve is usually what takes the wear, although it's a good idea to shine up the seat as well, if it's brass.

To touch the seat up you can use Comet (or any scrub cleaner) on a Q-Tip, then, work it back and forth. After it looks good, be sure to clean off all the paste.

Then stick it all back together and hold the float up on the end of a pencil (held horizontal) and if it stops the flow of gas, you're in good shape.
 
  #5  
Old 08-21-13, 07:04 PM
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A good band-aid fix is to install a manual fuel shut off valve between your tank and fuel filter. When you are done mowing, just turn off the fuel and your problem should go away. When you want to use the tractor again, just turn on the fuel valve and start her up.

The valve is less then $10 and takes maybe 5 minutes to install. Worth a try anyways and even if you later need to fix that inlet needle on the carb, it is always a good idea to have a fuel shut off valve anyways, for longer term storage.

You will need to blow out the fuel that is in the combustion chamber now with the method described to you by marbobj above and you should change the oil as well, right after you get rid of all that fuel.
 
  #6  
Old 08-22-13, 06:30 AM
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Thanks guys. I guess I need to back up and ask what valve and where is it as well as what am I too clean with the qtip? Is the valve the little part that screws into the bottom of the bowl and is that hole in the bowl what needs to be cleaned?
Thanks again!!
 
  #7  
Old 08-22-13, 07:03 AM
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Take off the bowl. There's a float in it that works up/down with the level of gas in the bowl. Up against the top of the bowl chamber is a little cross pin that holds the float on. Take that pin out and the little float valve will fall out. That float valve is what leaks as it seats against the seat it fits into. The valve is what you replace (kits are cheap) and the seat is what you polish up.
 
  #8  
Old 08-22-13, 07:13 AM
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No, the valve in question does not screw into the bottom of the bowl. To clean the valve you will need to take the float out. Connected to the float will be a small needle. That needle gets pushed up into a cavity (called the seat) when the gas fills the carb bowl. In working condition that push would seal the flow of fuel. In your condition, we suspect that valve is leaking. Perhaps there is some crud on the valve end or the seat that is preventing the valve from closing properly. This is a reasonably common condition on B&S Walbro carbs.

I doubt there is anything wrong with your battery. When that inlet valve leaks the fuel will flow into the carb, then into the intake chamber, then into the combustion chamber, flooding the motor. The motor will be very hard to start. It will either crank many times to blow out the fuel (choking will not help it here) or it will hydrolock a few times, making it look like your battery cannot crank the motor. This all depends on how much fuel has gotten in, which probably depends on how long it has been since you last used the motor.

I have seen this condition fixed with a simple fuel shut off valve placed between the gas tank and the fuel filter. What this does is prevent the fuel from flowing while the motor is not being used (usually the longest period of time for most people's tractors). This will prevent the flooding into your combustion chamber and yes, into your oil in your crankcase, diluting the needed lubrication. This oil must be changed, once it is fixed.

Obviously the optimum fix is to fix the inlet needle or seat, but you may find that the condition may just return in a few years, so I would want a fuel shut off valve on my motor, whether my inlet needle was working or not. Most likely in operation the valve is reducing the fuel enough to allow the motor to operate properly but if the float is stuck and the valve is completely open, then it will end up needing to be fixed anyways.

Here is a picture of a LMT walbro carb. In picture #6 it shows the needle we are talking about. Your condition is so common that this guy even shows a picture of defective needles. This is also a good guide to help you rebuild a walbro carb if you decide to go that route.

Disassembly, Cleaning and Repair of Walbro LMT Carburetor used on Briggs and Stratton Engines
 
  #9  
Old 08-22-13, 11:44 AM
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Thanks to both of you for your guidance.
Ok, I have got the needle out and when I was taking it apart, a little copper fitting (1/8 Inch long, flat on the larger end and concave on the other) fell out and I don't know where it came from or where it goes. I thought this might have come from the hole where the needle is seated but when I put it in there with the concave end up towards the needle, I cannot get the pin back in that holds the lever. Also is the the piece that needs the cleaning with the Qtip?

Too, when I buy a kit will it be the float (plastic) and all or just the needle.

Thanks again guys for your assistance.
 
  #10  
Old 08-22-13, 11:52 AM
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PS: And the needle is plastic with a rubber tip. Does not appear to be worn at all.
 
  #11  
Old 08-22-13, 07:21 PM
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The piece you saw fall out is the main jet. It goes down in the center of the white plastic insert. Small side in first.

Look at the white plastic insert on the opposite side of where the needle goes. There is an o-ring gasket there. Replace this gasket, as it is usually where the gas leak comes from when these carbs start flooding.
 
  #12  
Old 08-22-13, 08:54 PM
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Thanks Cheese. Does the fitting go down inside about 1 1/2 inch or on the opposite side where it just sits inside with the large side exposed?

There is no oring on this plastic piece. I do remember seeing one on the the carb and a section of it looked twisted.

I'm not seeing the seat the other guys mentioned. Where the needle goes, inside of there is all plastic.

MarbobJ wrote this: "Then purge the cylinder with the plug out to get the gas out (just spin it over a few times with the plug wire tied back to prevent arcing)." This confused me a little because if I take the plug out, would it arc if the plug is not near the plug wire?

Thanks much!!
 
  #13  
Old 08-22-13, 10:49 PM
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The plug wire can still arc without the plug in it. Don't want to light the gas that may blow out the plug hole.

The jet goes way down the inside of the long tube. If the o-ring is twisted looking, that's your leak.
 
  #14  
Old 08-23-13, 06:28 AM
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Thanks much. I'll replace the needle and the o-ring even though I don't think the needle is defective. Probably installing a shut-off valve too because this engine had been firing after switching it off, plus will be good for preparing for long winter storage.
 
  #15  
Old 08-23-13, 11:48 AM
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I went to get my parts from a lawn mower shop/mechanic and he said there was no twist in my o-ring. He did not have the needle part but went ahead and bought a shut-off valve.
Got everything back together/ oil changed and it cranked and ran rough. I drove it for about five minutes and it started running normal. I had only put a small amount of gas in just in case I needed to drain it again, forgot about the shut off valve. Anyway as I was putting gas in it to fill it on up, it went dead and will not crank now. I took the spark plug out and blew the gas out because you could smell gas. (Ironically, when I did this initially, as instructed, no gas came out.) Lots of gas came out on this last try. Changed spark plug too but still no fire.

What could cause this??????

Thanks again.
 
  #16  
Old 08-23-13, 12:52 PM
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While waiting I decided to take the bowl back off and do the pencil test, as suggested, to see if the valve was leaking. Pouring would have been a better word for it. No wonder the thing is flooding.

Can I buy the whole float part or do I just need the needle? Since I have been using the shut-off valve, does not seem that any gas has gotten mixed with the oil again, or would that be wrong also.

Thanks again for any replies and assistance.
 
  #17  
Old 08-23-13, 01:00 PM
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You'd have to take care of the leak first anyway. The shutoff valve will work fine to control the leakage during idle times, but the gas level in the float bowl affects the fuel air mixture. Without that fixed you have an overly rich mixture supplied to the engine.

Cheese mentioned an "0" ring as being the likely problem. Did you find that part? I just re read you post and see you have taken care of it.

In your case, the no fire is a flooding issue. When you get the fuel leak stopped, getting it started and running will be a simple matter.
 
  #18  
Old 08-23-13, 01:26 PM
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Thanks for the reply. Can you buy the whole float or just the needle? I could not believe how much gas it was letting into the carb/bowl. Also do you think gas got back in my oil? Cannot smell any on the stick and was using the cut-off valve. Of course during trying to crank the c/o valve was open.
Don't want to ruin the engine. Thanks again.
 
  #19  
Old 08-23-13, 05:19 PM
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That's probably a kit with the float and needle valve. The gas is coming from around the needle valve, and putting more pressure on the float doesn't shut it off? If the needle was plastic or rubber tipped the seat may just need a little polishing.

That engine probably only takes 1 1/2 to 2 quarts of oil. If the level was raised any at all by the gas, I'd change it. If you had gas in it, though it would have the smell of gas.
 
  #20  
Old 08-23-13, 09:03 PM
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The needle and seat rarely give trouble on this carb (the seat is plastic anyway). The o-ring is the usual culprit. If the needle is giving trouble, it's usually because a piece of debris is stuck in the hole, not letting it close properly. Check that, replace the o-ring even if you think it looks good.
 
  #21  
Old 08-25-13, 12:38 PM
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Maybe I am missing where this o-ring is. I see in my parts manual on the gasket float bowl, there is also a little ring pictured with that which may be the o-ring.
I don't remember seeing that little oring anywhere and can't find a pic online of the o-ring.
 
  #22  
Old 08-25-13, 07:53 PM
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Look in the hole in the carb where the piece sticks up into the bottom of the carb, it may be stuck there.
 
  #23  
Old 08-27-13, 12:35 PM
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Talking

Went and bought the gasket set yesterday with the O-ring. Where the 0-ring went, there was never one there that I saw and not up inside the hole in the carb, must have disintergrated. The guy who sold me the set looked at the needle valve and said it was not bad, just gently wipe it with gas when reassembling which I did. Had to change oil for the second time and replaced the o-ring and she is running again and grass is cut. So now I also am utilizing my shutoff valve.

Thank you guys so much for all the advice and hanging in there with me. Never really meesed with a carburetor but now feel a little more capable...with expert advice of course!! DoItYouself came thru for me again!!!!!!!!!!!!!
 
  #24  
Old 08-28-13, 08:04 PM
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Good, glad we could help. That o-ring must have fallen out while you weren't lookin'!
 
  #25  
Old 05-28-14, 02:22 AM
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Needle Valve/O-ring

Is the small o-ring that you speak of on the brass seat that the needle seats on?
 
  #26  
Old 05-28-14, 09:40 AM
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The needle doesn't seat on a brass seat on this. If yours does, it has a different carburetor. The seat is white plastic on the carburetor in this topic. If you have a brass seat, there is no o-ring to leak. Replacement of the needle is the only fix.
 
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