[Farmall] K5

[Bob Currie]

Amazing amount of work you put into that bigol K-5 Karl.  That F-20 tractor 
should sound like a Austin Martin now.

bobcurrie

At 09:25 AM 5/9/05, you wrote:
>Finally got the Zenith K5 carburetor on my F-20 back 
>together.  Complicated unit; it took a lot more work than I expected.  I 
>found a plugged-up economizer port, clogged compensator jet and an idle 
>jet with dip tube split along its entire length.  The bushing on the 
>driven end of the throttle shaft was badly worn.
>
>Got the parts cleaned up last week and painted the castings.  Let them sit 
>in the sun all week to dry.  Got the new parts from Gordon Rice, including 
>gaskets, throttle shaft and bushings.
>
>The throttle shaft bushing on the driven end of the throttle was blind; no 
>way to get behind it and press it out.  So I set the throttle body up on 
>my mill and squared it up relative to the mill table.  Used a small end 
>mill to cut away most of the bronze bushing in two places and then pried 
>the weakened bushing out with a knife.  While still set up, I cleaned up 
>the remnants of the throttle limit post, the thing that (used to) keep the 
>butterfly from being turned beyond wide open.  All that remained of this 
>stop was a rusty nub, so I milled it away and center-punched the 
>area.  Then I drilled and tapped it and replaced the stop with a 12-24 
>machine screw. This stop is important; it keeps the governor from turning 
>the carb throttle shaft too far.
>
>I pressed the new throttle shaft bushing into place, then used a 0.3125" 
>reamer to enlarge the bushing to the proper size for the throttle shaft. 
>With a new economizer valve (bushing) installed, the throttle shaft has no 
>play any more.  Nice tight fit.  Since I wasn't quite sure about the 
>orientation of the economizer valve, I used a cotter pin to fasten it to 
>the throttle instead of the recommended tapered pin.
>
>Since the original idle jet had a cracked tube, I borrowed one from a T-20 
>carburetor.  The original jet was a #14 and the replacement is a #15, for 
>what that's worth.  The orifice sizes looked pretty close.
>
>Put the carb back together using mostly new fasteners and reinstalled it 
>on the F-20.  All of the adjustment screws were open one turn, as 
>recommended in the manual.  The engine started on the fourth or fifth 
>crank.  After getting it good and warm, I adjusted idle speed, idle 
>mixture and high idle mixture.
>
>The exhaust is now clean at all speeds above idle.  At idle, it still 
>blows black smoke.  Maybe because I changed the idle jet.  The engine now 
>idles down nicely, which is one of the things it wouldn't do before.  I 
>noticed that opening the idle mixture jet seems to lean out the engine; is 
>this correct?
>
>Spent more than an hour driving around, listening to that wonderful F-20 
>sound.  I think we're ready for a parade.
>
>-Karl
>
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