Shifting Tech - gearbox secrets
 (or Marc Salvisberg gives it up......)

So.... you've looked at gearboxes for years and  inside the cases, they look pretty much the same.
Every brand's transmissions feel and work differently, model to model and even specifically, bike to specific bike.
One reason?

Check this part out -
If the Arms are centered, the trans tends to shift equally well, up or down.

If the fingers are closer to the pin that the shift shaft arm needs to grab to downshift, downshifts will be "quicker" and vice versa.
 

Good centering
Good centering		 This is usually good.

The pins are centered between fingers when the shift shaft is at rest.

If you look closely at the LH picture, you can see that I shimmed up the shift shaft centering stud with a folded business card, ~.024" offset made the difference.

Poor adjustment
Poor adjustment		 This is usually not so good.

The pins are not centered between fingers when the shift shaft is at rest.

If the fingers don't drop down fully, beyond the "pins", that prevents the "fingers" from dropping down and getting ready for the next shift.

If you've got issues - check.

 

  

Adjustable Center Shift Stud, 8mm       $24.95

(and possibly others that use 8x125mm threaded "fixed" stud)

1. Choose your shipping method

2.  
If the shift shaft fingers aren't centered on the shift shaft, Factory Pro has the fix.

It's a special 8mm thread, offset "centering" stud, adjustable by almost 1mm. For example, the difference in the above example was only .31mm/.024".

More experienced mechanics will recall when almost all transmissions were equipped with parts like these. That allowed the engine builder to set the shift shaft to exactly in the center for the best possible shift performance. We'd all like to think that the original engineers never make mistakes, but then we wouldn't need warranties, yes?

Install the stud with enough threads exposed for the locknut.
Turn stud till shift shaft "fingers" are centered on detent STAR pins.
Tighten down the locknut.
Recheck indexing.

This fits all the  DL650 / SV650 and others.

Actually, the "8mm stud assembly" is pretty common across different brands.
If doing your own experimentation, one of many things to look out for is the stud clearance to other parts - like the clutch basket.
You are "on your own".
Marc