Having found that my patched-up ribbon would not run through my caster’s air tower because of the low clearance under the raised air bar, I tried a different adjustment procedure to maximize the clearance available for ribbons in poor condition.
The Bar Length and Air Valve adjustments are the same as in the normal procedure.
Bar Sleeve Adjustment
This adjustment differs from the normal procedure in that it sets the length of the rod stroke to the longest possible amount which still ensuring that the ribbon stops moving before the air bar starts clamping.
The rod end 4G1 should still be clipped onto the pin 3G1 on the pressure lever. Turn the caster handwheel until the air tower lever is in its downwards stroke and the pawl ring lug has just stopped its counterclockwise motion against its stop screw.
Loosen the Bar Sleeve locknut, and screw both the locknut and sleeve clockwise (down) until the sleeve and its washer are no longer against the underside of the lug on the air tower side cover. Now carefully turn the sleeve counterclockwise (up) until the sleeve and washer just contact the underside of the lug, then give them one more turn. Tighten the locknut.
Verify that the pin on the end of the paper tower lever still has some downward travel before hitting the end of the slot in the lower end 4G3 of the rod by carefully watching it while the handwheel is advanced a few degrees. There should be about 1/32″ travel (from the one turn of the sleeve).
Air Bar Pressure Spring Length Adjustment
This differs from the normal procedure in that the spring length is adjusted to ensure a particular amount of spring compression, leaving the rest of the pressure lever movement for raising the air bar.
With a ribbon loaded in the air tower, rotate the caster handwheel until the pin jaws are closing.
Use a pair of wrenches to loosen the two locknuts 2G7 without loosening the studs 2G4. Turn the adjustment screws 2G6 clockwise by hand until they contact the pressure bar. Turn them back counterclockwise ⅓ turn. Turn the locknuts until they contact the adjustment nuts, then hold the locknuts steady while you turn the adjustment nuts counterclockwise against them to lock them.
Having done the adjustments this way, my lumpy ribbon seems to run through the air tower without jamming, at least when done by turning the ribbon feed wheel by hand.