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Hot!New Carb Won't Idle

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2019/08/04 10:11:59 (permalink)

New Carb Won't Idle

I have a Craftsman 358.794730 25cc leaf blower.  No longer made, but it looks identical to what's sold under several brands and is the older version of this:
(Edit:  I can't yet link to this  newer Craftsman 41AS99MS799 that it looks like)
It uses a Walbro WT-875 Carb.  Started running extremely rough, hard to even start.  As old as it was (around 10 yrs), I bought a generic carb kit including filter, fuel line, spark plug, carb & more, replaced all these items plus smaller fuel line that didn't come in the kit.  Here is the kit: 
(Edit:  the carb kit is called a  Carbhub WT-875 Carburetor for Craftsman Poulan Pro Blower BVM200C BVM200VS P200C GBV325 P325 with Fuel Line Filter Gasket Spark Plug Replace 545081855 WT-875 WT-875A ), pictured below.
Still ran rough.  Pulled muffler off and saw cylinder exhaust port was practically blocked.  Cleaned that out and it runs good at partial and full throttle but won't idle.
I turned the idle screw out 1 turn, no difference.  Can't really tell when the idle screw is fully seated, seems like the threads in the carb for it are pretty sketchy, poorly cut and it's loose.  Turned the carb screw out more, and more, and it still won't idle.
It wouldn't even bother me if it idles high, just want to get it to idle.  The carb is past the return period and I'd like to keep using it if possible.  Is there some easy way I can check or modify it to get it to idle even if i lose the idle adjustment and/or it idles  high?
Can I take the carb apart and put back together using the same gaskets or are they one time use?  Once apart what do I look for, or should I stick a piece of wire down the hole the idle screw sits in or spray carb cleaner down that hole?   If the screw is really loose would this create a vac leak and I could lather some silicone grease on the screw or just plug its hole entirely with epoxy?
I guess if I have to, I'll just put the old carb back on but I hate to put an all original 10 year old carb back on and would like to learn what is wrong with the new one already on it.
I do have a drill press and tiny carbide PCB bits, etc, if that would help?   I mean if I just enlarge or clear out the hole that idle screw is metering (I mean the internal tube or jet or whatever it's called, not drill down through the idle screw hole), is that a slam dunk to get it to idle or is it possible that a little enlarged hole would make the mix too rich to idle?  Should I instead run something soft down through that passage like plastic monofilament (like fishing line but thicker)? 
I'm wondering if the idle screw threads in the carb body are horribly machined, got chewed up and sheared off creating a blockage.  Externally nothing looks wrong with the carb besides the looseness of the idle screw.
post edited by Dave9 - 2019/08/04 12:23:12

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