Originally Posted by gjscott
Yes. Are you sure there's 9 ? not 8 ?...
Yes, there are some rotors with 9 buttons
Also I think I counted 9 spots to place the magnates should I use all 9 or will that mess things up?
No, you cannot use 9 and get correct reading - and you should not use 8 of those 9 either as that extended 'space' will throw things off.
Your options are
1) to not use the the button locations and try to space equally at 45 deg intervals around the rotor at another mounting point;
2) use 9 and live with the speedo error - it will be about 12% fast over & above the already inherent factory 'fast' indication - probably about 20% over actual speed will be indicated.
3) use 9 (or 3!) and install a speed healer device - expensive, but probably best option.