Karl Townsend wrote:

here's a pic of a similar unit:
http://www.jacto.com/sprayers/agricu...arbus_400.html

Ah. Looking at that, it brings up the question of the spray pump. If
there is a problem with the triplex pump with one cylinder not working
for some reason, you would get a lighter load each time that piston was
supposed to be on it's pressure stroke, possibly allowing the flywheel
effect of the blower to drive the pump ahead of the PTO drive
momentarily with the PTO catching up a fraction of a second later
causing the drive line to experience the forward - reverse bucking you
noted.