From: Jim (W7LS@BLARG.net)
Date: Mon Jun 13 2005 - 11:38:02 PDT
Thanks to all who offered suggestions. I can describe the system a little more, here.
There is a speed sensing output similar to a speedometer takeoff point, that is located back at or by the transfer case. It spins a cable shaft similar to a speedometer cable, which feeds forward under the cab, to a point underneath the carb, on the passenger side (er, "soldier B" side). The spinning cable spins some weights in a centrifugal arrangement whereby this governor yanks on a cable that opens a second set of butterfly valves underneath the carb. Yes, there are two sets of butterfly valves in this arrangement. One is the set normally found in the carb. The second set is where you would normally find a carburetor riser block.
This sounds fairly straightforward up to here, but there is another module between the governor and the lower butterfly valves that has a vacuum modulator in it. However, the vacuum was being derived from the aircleaner! Maybe someone in the past has mistakenly hooked it on there, instead of where it would sense manifold vacuum. No book, so no idea.
It would appear that the PTO shaft speed was thereby yanking open the lower butterflys against an adjustable spring, such that a constant 1700 rpm engine speed was maintained (assuming you are in 5th gear, as the operator's manual commands). Then why is there a vacuum modulator in there to alter this balance of power (well, force)?
The cable that runs from the governor to the lower butterflys is odd, too. It's not a simple cable. It looks like the attachment points on the cable belie a method of adjusting the length of it. The cable ends have a spiral wrapped wire around it that looks like the setscrew that affixes it can be placed at several discrete points for tuning. Curiousier and curiosier..... Rube Goldberg would be proud.
So there you have it. If anyone has printed or cerebral info on this, I'm all ears! :-) Thanks. Jim
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