Originally Posted by
buildabikews
Consider me a lucky man, well, at least partially lucky as I do still have a gear ratio issue. Attaching pics of my small white manual, and this machine also has a chart plaque on the machine that matches the manual. I had considered just calculating the gears I would need for each thread pitch, but the issue I have is that they end up being gear combos that I don't have, or worse, can't purchase.
I did notice in some other pics people put online that the gear coming out of the headstock is more course and has around 18 teeth. You mentioning that this machine was one of a few that had a fine tooth output made me think about the fact that the ST86 shift lever attachment that was added probably has a gear ratio set up for a machine with a course thread gear at the headstock and that may be incorrect for this machine.
My lead screw has a course 30 tooth gear and connects to the gear arm via a course 27 tooth gear (you can see this in the recent pic). Did this "rare" early build have all fine tooth gears and the course one that are in it now would be from the aftermarket purchase? Remember earlier in my post that I said I have a couple of gears with tape on them saying "not sure what these are for"? Both of those are similar in size to the forward/reverse gears on the new plate, but they are fine threads, not course. Could those be the originals that came with the machine? Did the lead screw gear have fine threads as well, the one I have currently is course and wouldn't match up with those fine gears.
If I recalculate the gear ratios, replacing this course 27 tooth gear with a 21 tooth will give me the proper ratio. If Shopmaster sells this, then that would solve my problem.