So I have been fighting with down shifting issues on and off for about a year. Ironically I had no issues until after having the dealer replace the shift mechanism as part of the recall.
About 6 months later I noticed that I started having issues downshifting from 4th or 5th. I would click the pedal down but I would remain in the same gear as before. It eventually got to the point that it was nearly un-rideable. I poked around the internet and found that no one had a solid answer. I even asked the local service manager and he didn't have an explanation.
So I took the bike apart myself because I really like to know how everything works and wanted to make sure that the dealer really had done the service. After taking the clutch out and poking around I saw how the mechanism worked and that it appeared to be slipping. I removed the mechanism and took it to the dealer. The service manager gave me a takeout part from a new bike. I dropped that part in and the bike shifted great again... until this spring.
Now passing 20K miles I am familiar with how the bike shifts, how much pressure is needed and when to add some clutch.
I decided I had enough after doing an entire track day in 4th. I could still shift down if I eased it into lower gears slowly. So apart it came. I ordered the race-kit star wheel for good measure. When I pulled the shift mechanism that I had put in there I noticed that the 'fingers' had substantial wear on them It had only been in the bike for about 6 months.
I put the race wheel (smaller neutral notch and re profiled first-second lobes) and the warranty replacement part back in. Now it doesn't want to shift at all... total junk. I'm getting afraid that I messed up the shift forks and internals at this point.
I pull the cover and clutch once again and start really diagnosing the problem. This is when I start taking the videos to analyze frame by frame what is going on. I replicate the action outside of the bike and really spend some time working out what tolerances and manufacturing/wear defects could be causing this issue.
Here is a short video of the mechanism in action:
So finally I take the warranty part that has the properly hardened 'fingers' and attack it with a Dremel tool. I strategically removed material to allow the 'fingers' to engage the star wheel more positively. I didn't want to remove too much so I re-assembled and tested it three times before I get the tolerances just right.
The distance between these two lines needs to be reduced:
So I removed material from the areas that are circled:
Until I could no longer see daylight: (and then a little bit more as it turned out)
For those of you counting I removed the side cover and clutch around 5 times in two days.
Now it shifts flawlessly and positively. With all the other work done to it in the last few months I couldn't be happier!