This recently happened to my niner. I have the new sensor and will be cutting an access hole rather than removing the air box.
Funny thing about plans... they tend to change.
Long story short I didn't cut an access hole in the air box, and I did not remove the air box either. An abundance of time to think about the situation had left me determined to replace the speed sensor without resorting to drastic measures.
This last Saturday (9/19... go figure) I replaced the clutch cable on the Niner, and once that task was complete I decided I would sit down and get serious about figuring out how I was going to get the speed sensor replaced without pulling or modifying the air box. After a little poking and prodding of the cables and hoses around the sensor I realized it was very likely that if I could get the bolts out, then there would be JUST enough room to lift out the sensor by tilting it to the left as I was lifting it up and out of it's seat. All that needed to happen was to move a few cables out of the way and hold down the hose on the left to make room as I pull out the sensor.
Getting the front bolt out would be easy enough, but reaching that one in the back? Yeah. That was going to be interesting. I pondered many different options concerning how to reach it AND get it broken loose. All manner of crazy gadgets and contraptions were considered but finally I settled on an unlikely tool that happened to be perfect for the job.
So what was this mystery tool? What makes it so great? That, my friends, I shall leave till the end of this write-up. Partly because I think a little suspense makes for a good entertaining story, and yes partly because sometimes I'm just an onery ass. Yes, yes... I am well aware that one could just skip to the end, but where's the fun in that? Being riders, I'm sure we can all appreciate that it's more about the journey than the destination!
Okay enough of my rambling. I'll get to it.
As it turned out, my initial hypothesis was correct. I was able to get the cables moved out of the way and the first bolt came out without any issues whatsoever. I then used my mystery tool to access the second bolt in the back by reaching in behind and over the swingarm pivot area. With a little elbow grease, the rear bolt broke loose as well and I was able to get it loosened with my fingers, and hauled out with a pair of long needle nose pliers. After that it was just a matter of disconnecting it's wire from the harness and using a flat head screwdriver to pop it up out of the hole. As stated in my educated guess earlier, all I had to do was hold down the hose on the left as I lifted out the sensor, tilting it to the left so it could go into the space left by the absence of cables and the hose. After that was done, all I had to do was pull it out and I was left with this:
Sensor popped right out.
Now all I have to do is dump the old sensor and install the new one.
All I had to do was reverse the procedure at this point. Tilt the bottom end of the sensor toward the hole, press down the hose again, tilt the upper body of the sensor left and fit it into the space left by the absence of the hose and cables, and guide the new sensor down into its seat.
I then used the needle nose pliers again just to make it easy to set the front bolt back in place, and then tightened it with my fingers just enough to hold the sensor in place.
Now it was time to do the same for the rear bolt. Again I used the needle nose pliers to set the bolt in position, and then I used a long slim flat head screwdriver inserted from the right to slowly spin the bolt down by pressing alongside the bolt head to cause it to thread in.
Now that both bolts were snugged into position, it was time to actually tighten them down. The front bolt was easy enough, of course... but what about the rear? Enter the mystery tool!
The tool is an open end / box end wrench. Not very glamorous, but this one is just different enough to matter for this task. It has the correct length and angle to reach the rear bolt from the rear of the bike. All I have to do is use it to reach in and get hold of the bolt, and a series of short turns gets the job done.
All tightened up! At this point, all that was left was to connect the new sensor cable back into the appropriate location on the wiring harness. Replacement complete! I then put all the cables and such back in their original locations.
All done! Just like new... kinda.
So what was so special about the wrench? Just the right design and dimensions was all, but no regular wrench would do the trick. This 10mm MAC wrench seemed as though it was made just for this job. The photos below will make it pretty clear why it worked so well, and should aid anyone who may be looking for one, to get the right one. The "deep" and angled box end makes it work for this application.
That about covers it. I guess this concludes the story of how I managed to replace my speed sensor without drastic measures. I would say the whole process could be done in about 30 minutes.