Help with 520 carb

[Deere_Man]

I thought I would help a neighbor by rebuilding the duplex carb on his 520. I started by buying the videos from Roberts and watching it so I would understand what was going on. I put it back on and it didn't run quite right. I noticed at idle if I turned the right needle it affected the way the tractor ran up to even killing it. If I turned the left nozzle it had no effect. A fast idle it backfired and just wasn't right. I pulled the carb back off and dis-assembled it again. I pulled out the channel balls that are in the bowl along with the two in the back by the throttle plates, and didn't really get anything out at all with the drill bit (I done this the first time as well). If I squirt carb cleaner in the back holes where the channel balls were it comes out full stream of the welch plugs. My question is what else do I need to ensure is clean? I can't get wire through any of the other tubes which I suspect is just due to the geometry of the other passages (using .020 wire). What next? I just don't want to do this again.
Thanks!

 

[PopinJohn]

It sounds like the carb is still plugged up, OR you have a vacuum
leak, maybe in the manifold itself. If problem is in the carb.....
The following idle circuit orifices and passages must be open.
Each nozzle chamber has a .040 orifice going into the .094
passage parallel to the main nozzle chamber, passing to the
welch plug opening on each side of the body.
Looking toward the venturi through the choke end, there are
four air vent orifices that must be open.
At the throttle end, each .094 passage (from the welch plug
area) has one (sometimes two) .040 orifices passing into the
throat just forward of the throttle blades. The steel plug in the
body above the throttle blades must be removed to properly
clean these tiny holes and they must not be oversized.
Not the same as the orifices for the idle mix needles.
We have also seen an unseated welch plug on the side of the
body cause a vacuum leak.
The tractor should run properly with both idle mix needles about
one and a quarter out under normal conditions.
www.popinjohn.com

 

[jason1816]

make sure you have spark on both sides first.. might have a valve hanging up too..

 

[Deere_Man]

John-I went through all of the passages you described today and ran a wire through all of them followed by carb cleaner. I'm certain none of them were plugged. I didn't want to do this but I think I'll put the carb back together and put it on my 50 to see what it does on it. My 50 is in it's dress clothes so it will be hard to put the carb on it without scratching something. I think this is the only way I can prove that there is something else wrong with the 520.