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Along the same lines, Murphy also enlarged the idle downtubes (the brass piece being drilled here). Stock sizes vary from 0.026 inch to 0.042; ours were drilled out to 0.038, which will help our new mill get the fuel it needs at idle. The carb's channel-restriction orifices were also spec'd out. These openings intersect the mixture screws, ultimately controlling how much fuel gets through during idle. The orifices measured 0.049 inch, which was acceptable for our purposes.
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Along the same lines, Murphy also enlarged the idle downtubes (the brass piece being drilled here). Stock sizes vary from 0.026 inch to 0.042; ours were drilled out to 0.038, which will help our new mill get the fuel it needs at idle. The carb's channel-restriction orifices were also spec'd out. These openings intersect the mixture screws, ultimately controlling how much fuel gets through during idle. The orifices measured 0.049 inch, which was acceptable for our purposes.  View Related Article

 

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