Richard's ST2 pages - JohhnyB's shifter fix info

In this photo the linkage is in the "Locked in 2nd gear mode" which of course is undesirable. Look closely at the actuator arm and the shift drum. See the foot coming off the lower side of the actuator arm? Notice the pin on the shift drum which is to the right of that foot, there lies the problem. The actuator was allowed to move too far the left which slid that foot to the left of the pin. Normally the pin would intersect the middle of the foot and rest on top of it. With the linkage in this position the actuator arm is prevented from moving to the right by the pin on the shift drum and prevent from moving the the left by the shift shaft backing plate tabs, one of which can be seen at No. 4. The tab that is preventing movement to the left is actually behind the flywheel where it can not be seen in the photo.

Here is a close up view. Regardless of how it appears in the photo the foot at No. 2 is a 90 degree bend towards the inside, the "sole" of the foot is just long enough so that the lower portion of the arm can slide past the shift drum pins. However as you can see here the "sole" of that foot is trapped behind the shift drum pin at No. 2. In the No. 1 location you see the upper portion of the arm where it engages the shift drum pins and does the actual shifting. It has a hook on the end which is hidden behind the pin plate (the pins extend through this plate) this hook grabs the pins and can rotate the drum to the left as the arm moves to the left. See the "armpit" of the upper arm where the lower arm starts? That notch grabs the drum pins and will rotate the drum to the right as the arm moves to the right. All of this works in kind of a racheting motion. The hook on the end of the arm will slide over the pins in one direction but will grab the pins if going in the other direction.

In this not so clear photo you can see the mechanism in it's proper, working orientation. Notice that at No. 1 the shift drum pin is now sitting on top of the "sole" of the foot, instead of being to the right of it. This arrangement lets the upper actuating arm rotate the shift drum to the left, BUT, only until the next pin contacts the top of the foot. This both allows enough movement to shift the gearbox and also prevents the drum from rotating too far.

At location No. 2 (s) you can see the two shift shaft backing plate bolts, they are each a different size. They go through slotted holes in the backing plate and into the crankcase. You can loosen these bolts, place a screwdriver blade between the backing plate and the crankcase at location No. 3. A gentle pressure will move the backing plate. You will notice that the entire mechanism, actuating arm and all will move as you do this. This adjustment allows you to center the "stroke" of the actuator arm across the drum pins. You want enough stroke to the left to down shift cleanly and enough stroke to the right to up shift cleanly. I discovered that an easy way to do this is to adjust the backing plate so that when in second gear the lower shift drum pin sits squarely on top of the center of the "foot"

Here is a photo of the linkage in the proper configuration for neutral. No the "foot" in not extending into the hollow shift drum although it looks that way. Want to know why neutral is hard to find sometimes, you can see that no pins are contacting the foot and that the upper arm seems to be grabbing the top right pin with one hook and the top left pin with the "armpit", which is exactly what it's doing. Neutral is "between gears" so there is no REAL positive stop, just the action of the shift drum detent mechanism to keep it in this position.