B&S 16.5 carb rebuild question...

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Old 04-02-12, 07:38 PM
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B&S 16.5 carb rebuild question...

I've got a lawn tractor with a Briggs & Stratton 16.5 engine and I notice the smell of raw fuel after I have used it.

It's about nine years old. There is a thread on this forum where someone had a similar issue (http://www.doityourself.com/forum/ou...h-muffler.html) and he rebuilt the carb and still had the problem. He then replaced the float and that fixed it although the old float did not appear to be bad.

Should I replace only the float and see if that fixes it or would it be best to do a rebuild first? In other words, would it be silly to replace the float and not do a rebuild on a carb this old?
 
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Old 04-02-12, 10:31 PM
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Well, I think the first thing to do would be to find out where the smell is coming from. Could be a gas line, leaking tank, several things. A leaking carb usually doesn't give the smell of raw gas directly after using it. More like after it has been sitting for some time.
 
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Old 04-03-12, 05:55 AM
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A leaking carb usually doesn't give the smell of raw gas directly after using it.
Sorry I was not clear on my post. Yes, I notice the smell after it has been sitting for some time and not immediately after I shut it down.

I did look at the tank and lines and fuel filter and see no signs of leakage. And if those components were the culprit, it is likely the smell would continue until all fuel has leaked out. In my case, the smell is gone after a few days.

Plus, there is a lot of oily-looking dirt in the immediate area below the carb, indicating to me that the leakage is there - as if the residue from the evaporated fuel is collecting dust and dirt.
 
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Old 04-03-12, 05:40 PM
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Okay, that sounds more like a leaking needle as you suspected. I'd suggest replacing the needle, bowl gasket, and clean the carb. Check the oil for a gassy smell as well. If it is thin and smells of gas, change it.
 
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Old 04-03-12, 06:49 PM
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that sounds more like a leaking needle as you suspected
I'm confused by that - I thought the issue could be a bad float.

If so, should I replace the needle and bowl gasket as you suggested first and see if that fixes it...

OR

should I replace those two items and the float all at once?

Thank you for your help!
 
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Old 04-03-12, 07:20 PM
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Yeah, I didn't go back and read that it was the float you suspected. If the float was bad, it would cause the needle to open and leak, which is what I was referring to. The float should be good. The needle is what shuts the gas off to the carb and is what commonly leaks. If the float was bad, the needle would open and allow the carb to flood badly. You would know something was bad wrong by the gas dripping all over the place. Yours is more of a slow seep, and the needle is the likely culprit. I suggest replacing the needle and clean the carb. The bowl gasket often needs to be replaced once the carb is opened, so I recommend replacing it. If your carb has 2 screws holding the bowl on, the bowl gasket is a little different. It will be an o-ring type material gasket that is formed to fit the grooves in the inner assembly. Replace it and the o-ring that comes with it that goes over the area where the float needle goes in. If your carb only has the center bolt or fuel shutoff solenoid holding the bowl on, then just replace the needle and bowl gasket. In both cases, soak a q-tip with carb cleaner and clean the area where the inlet needle goes, all the way to the bottom where the rubber tipped needle seats.
 
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