Surging after rebuild

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Old 04-10-09, 05:04 PM
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Surging after rebuild

The Walbro carb on the Murray (13.5 hp Briggs) is surging the same after the rebuild. Here's the thing....last night after I reassembled it, it ran like a top, no surging after a few seconds of warm-up. Ran fine at all speeds, tonight I was going to warm it up to change the oil again and it was surging the same before I had the carb cleaned.

Welch plug removed all was cleaned, in the rebuild kit, there are 3 different jets (I assume thats what they are) that screw inside the carb body under the bolt that holds the bowl in place. They all have the same number of holes in them but why 3 of them?? Are the bores in the center just slightly different depending on altitude? They all appear to be the exact same, hard to tell any differences if any.

Maybe a piece of trash got sucked back in....dunno, the limiting screw that controls the idle mix I assume, wrapped in black plastic and only able to turn it 3/4 turn....what is the proper way to adjust this?
 
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Old 04-10-09, 06:03 PM
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Did you check/clean the fuel tank ? Replace the fuel filter ? Flush the fuel line ?

Sounds like it got trash back in it if it ran good the day before, You can remove the plastic cap on the adjuster to fine tune it better but that's only for the idle circuit.


Good Luck
 
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Old 04-10-09, 06:54 PM
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After I cleaned the tank originally, I sent my BIL to the store to get some fuel line and a filter. Could the fuel line not be rated for fuel? Doesn't say anywhere on the hose the word "fuel"...hopefully the guy didn't cut him regular vacuum line but I don't know if they are the same or not.

I removed the carb and sprayed every passage out and it runs smooth again. My bet is on the hose breaking down since there were alot of very tine dark specs in the bowl...very tiny, almost like dust.
 
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Old 04-10-09, 07:24 PM
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Most black fuel hose has a thicker wall and has string embedded in the wall. Most black vacuum hose is thin walled with no string, Tygon hose is yellow in color with a thin wall without string but is rated for fuel.

There could have been trash in the hose from sitting on the shelf, Who knows..... That's why it's best to let a little fuel run through the hose into a container before hooking it to the carb....
 
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Old 04-10-09, 08:33 PM
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I let alot drain, about 1/2 gallon. Let the fuel sit, then drained it. Let it sit overnight and picked up a little residue and turned a dark yello then I drained some again. It's now clear even after sitting for a week but I did drain some more before I started it and that's when I noticed the residue in the bowl.

Like you said, still prob some trash in the new line, hopefully it will work itself out.
 
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