The shift drum rotates between the gears and the boss,pawl,star,thing on the end has to ratchet the drum in alignment for the different gears,the boss has to drive and return for each shift. All the parts of the shifting have to be in proper orientation to each other to work properly.The only way is to put the trans in neutral,make sure the boss is centered and slide the spindle in,centering the teeth on the fork and boss. With a pair of smooth jawed channel lock pliers you should be able to get it to shift,rock yhe entire drum and rotate the counter shaft sprocket at the same time. Spinning the drum in a counter clockwise direction should end up in 1st.