Hello, I know this may be too late for original discussion, but I for one frequently find myself getting to these posts later while researching. I just want to say that yes it is unsettling to think of rear brake no spring! I actually bought one that was for another rearset. I just searched web for rear brake spring hayabusa and found one that fit on the actual brake cylinder! It works perfect you just slide an open end wrench to adjust lever position no problems. I have plenty of return pressure just like stock so don't worry. The spring has an opening on one end that matches the adjuster bolt and flares up to fit perfect into brake cylinder. Like it was made for it. All you do is lossen adjuster nuts and take off fitting then slide on spring and reassemble then adjust lever to new rearsets and your done. Looks way better too!