Most parts are readily available, though from what I can find, I've got an older gearbox with the nut on the countershaft and this 2nd gear arrangement which is no longer in production.
I wonder if the 2nd gear from a AX15 works with the older style syncho/hub in a R151F.
That gear has 33 teeth, same as the one in the R151 and the AX15 is pretty much an R series transmission.
