This may be of some help.
While you are working on the cylinders consider changing the valve timing from "Outside Admission" to "Inside Admission" (It is mentioned in the link) as it evidently improves forward running.
I still have to adjust mine just have to get around to it.
ACCUCRAFT RUBY ADJUSTMENTS by Dave Hottmann - PDF Free Download
ACCUCRAFT RUBY ADJUSTMENTS by Dave Hottmann Oil the reversing valve and slide it back into the valve assembly. Then screw the reversing quadrant to the deck plate using two M2 x 4 screws. Note that you
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I still have to adjust mine just have to get around to it.