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PLEASE HELP 560 Carb Experts

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big a

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Been working on this for a week or better with no luck. Tractor was sitting for 10 years or so, and I have no idea how it ran before. Soaked carb for a week, blew everything out and replaced needle.and seat. Idle jet appeared to have been drilled, so replaced it too. Float is set to factory specs, and not leaking.
The engine is running rich at idle, but normally once off idle. Smokes black at idle and idles rough. I noticed at the initial tear down that the idle needle was completgely closed. Seems to run best with it closed....but even better with the idle screw removed completely. You can feel slight vacuum with your finger over the opening, and when covered, it runs richer.

Heat riser is working, new plugs and been through the distributor. I suspected damage to the the idle needle seat, so marked the needle with a marker and screwed it in....leaves a nice even mark on the needle.
Anyone have any ideas here?
 
Forgot to add, this has the early double venturi. I was able to remove it, and verify that the small bleed ports above it are clear too.
 
If the idle jet was drilled out the main jet may
have been drilled also and some times when that
happens you cannot control fuel even by turning
the main jet adjustment all the way in as it does
not conform to the taper on the needle. You should
be able to kill the engine when running by turning
the main jet needle adjustment screw all the way
in. If you cannot then you know where to look.
If you can it still might be the jet is over
sized. I don't have the jet size in my head but it
is about .050, and I have seen then drilled out to
double that. All fuel has to flow through that
main jet at all speeds and loads. It could be the
main nozzle is messed up also but you would have
to compare it to another one to tell. I am
assuming air intake from air cleaner is not a
problem but that is easy to determine with hose
off air cleaner.
 
Thanks Pete. I'm just back from a quick trip to the shop, in my underwear! The main mixture screw was bottomed out against the packing. I reinstalled the old packing, readjusted it and it ran like NEW!
THANKS to you, and all the others who offered help with this.
 
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