Dunno about the Minnie, but my Allchin water pump drive is off the crankshaft. The lubricator drive is off the valve spindle so the ratchet stroke is altered by the position of the reversing lever. If the stroke were to be too small, the drive wouldn't pick up a new tooth. I can't see that being an issue as the engine won't run with the valve gear in that position anyway. As long as the pump works with the cut-off at a working position., that's OK.

Hi Terry; "cut-off " applies to the valve movement as adjusted by the reversing lever. Full movement gives steam admission for 100% of the piston stroke, (100% cut-off). Progressively less as the lever is moved towards mid-position. My point is that since the engine won't function at small cut-offs, say 25- 30% minimum, it doesn't need lubrication for that situation.

Clive

What Clive said, as the reverser gets closer to neutral you will get progressively less movement of the valve rod and as that is what drives the lubricator you won't get enough movement of the arm to engage the next notch on the ratchet.

If your engine won't stop then your regulator is letting by

May need lapping or could simply be that the linkage is a bit short and not allowing the regulator to fully close or the puck is tight in the buckle so not able to seat well on the port face.