Where does the Speedometer read from?

[rain]

I spun the front and rear wheels, (key on, of course, engine not running), and it still read zero.
Keeping in mind that spinning the rear also spins the transmission output shaft, etc., how can this thing be measuring speed?
 
A while back in another thread someone said they changed sprockets, and the speedo still read accurate. Any ideas?

[stuna]

from the trans if you change gearing , your spedo will be off 

[gabefzr6]

I thought it read from the ABS sensor on the rear wheel.

[nsmiller]

I thought it read from the ABS sensor on the rear wheel.

I'm pretty sure this is correct, because if you cold start the bike in neutral on the center-stand the rear wheel will spin due to oil drag and the speedometer will register a couple mph. Pressing the rear brake brings the indicated speed back to zero.

[wessie]

I thought it read from the ABS sensor on the rear wheel.

Yes, the service manual says to check the rear wheel sensor if the speedo is not working
p8-26 

[betoney]

from the trans if you change gearing , your spedo will be off 

I changed the countershaft sprocket from 16T to 15T and he speedo didn't change.  I verified with a GPS on stock gearing and then with the changed gearing and both showed a difference of about 1 mph at 70mph.  

[stuna]

then it was changed from the fz . as it did not have abs 

[adjuster]

SO,no need for a speedoDRD. (Speedo healer.)
 
My FJ09 seems to be pretty optimistic on speed, a few MPH faster indicated than actual.
 
Anyone else have that same reading?
 
The only way to really change speed then is with tire diameter, or the speedoDRD.

[nsmiller]

SO,no need for a speedoDRD. (Speedo healer.) 
My FJ09 seems to be pretty optimistic on speed, a few MPH faster indicated than actual.
 
Anyone else have that same reading?
 
The only way to really change speed then is with tire diameter, or the speedoDRD.

Japanese bikes have always been relatively optimistic on speed. Some have been pretty awful, being off by as much as 8 or 9 mph. I think the FJ-09 is no more than about 2 or 3 mph off of what GPS indicates regardless of speed. What I mean is that it is 2 or 3 mph optimistic at 35 mph and still 2 or 3 mph optimistic at 85 mph. Compare that to some other bikes where the error in the speedo gets worse the faster you go. I consider the FJ-09 to be relatively accurate. Certainly its accurate enough for me. Probably good insurance for me in case a cop should point a radar gun at me.

[owle]

I've been checking the accuracy of my speedo, and its way out in the upper speeds, at an indicated 30 GPS 27 50/46 70/65 80/74 130/122.
 
It's interesting that people seem to have different readings from the same bike, i know that we all have a margin of error in our results, but there seems to be a large discrepancy in results to put it down to human error. Anyone know if you can calibrate the speedo, as its not a cable/mechanical drive.

[bobaintstoppin]

2 Wheel Dyno can correct speed error as part of a flash.  Mine was off by only 2mph so we didn't do it.  You might want to call him and see how he wants you to confirm your error before he makes changes.

[owle]

2 Wheel Dyno can correct speed error as part of a flash.  Mine was off by only 2mph so we didn't do it.  You might want to call him and see how he wants you to confirm your error before he makes changes.

Thanks, so calibration can be done, i'm in the UK and recently had my ECU flashed, this was not one of the options mentioned, good to know for future reference. 

[rain]

OK, OP here. I was wrong about the speedo not registering when the rear wheel was spun, I just wasn't spinning it fast enough for it to register 3mph. It does.
All this was leading to some sprocket changes I was considering. I swapped the rear 45t for a 43t. I was also going to do the front UP one tooth but that chain guide is in the way and I'd have to mod it or leave it out. So for now I figured I'd just see what the rear change was like. It's about 4.4% taller.
BUT THE WHINE WAS DEAFENING. From about 25mph up it started, and just got louder and higher pitched as I accelerated. I wasn't sure if it was the chain rubbing on the chain pad on the top of the swingarm, or just the chain/sprocket itself. Seriously, it souded like a cop siren, and from about 35mph on up to about 70 when the wind noise finally drowned it out, I couldn't even hear the engine.
So as I headed up to Alices Restaraunt, I wondered if maybe I put the sprocket on backwards or
When I got there I inspected and all looked well. Had a friend sit on it and the chain was too tight, in the order of about how tight it was when I bought it, but it didn't whine with the OEM sprocket, so hmmmm.
On the way home it got noticeably quieter, maybe by a third.
When I got home I loosened the chain and rode it again. This time it was quieter by another third. I'm thinking it's just this sprocket wearing in...?
Anyways, I like the new gearing, don't think I'll go up a tooth in front for now.
2 takeaways from this would be 1) The speedo accuracy isn't impacted by re-sprocketing, and 2) The bike's already whiny demeanor is nothing compared to a noisy sprocket.
(sprocket is a SUPERLITE (#12815R) RS7 Series 525 Pitch Steel Rear Sprocket - YAMAHA 43T SL12815R-43 from sprocket center.

[betoney]

2 takeaways from this would be 1) The speedo accuracy isn't impacted by re-sprocketing, and 2) The bike's already whiny demeanor is nothing compared to a noisy sprocket. (sprocket is a SUPERLITE (#12815R) RS7 Series 525 Pitch Steel Rear Sprocket - YAMAHA 43T SL12815R-43 from sprocket center.

I have the same sprocket except I went to a 15T, -1 from stock and it whined like that for awhile until it wore in.  I cant imagine changing to higher gearing like you describe, the engine has such a wide powerband and pulls so long in each gear already, I had to lower the gearing to make the engine a bit more responsive and lively. 
 
This is an excerpt from a ride review my brother wrote after riding my bike with the 15T sprocket.
 
"The engine is the most impressive part! I told Brian that as I was riding it I kept thinking either the tachometer, speedometer or gear indicator must be wrong. We were going through some sweeping corners and I was keeping the engine where it felt best. I looked down coming out of a corner and I was passing 70 mph, but I was still in 2nd gear! I opened it up a little bit on a straight and it got up to 100 and I noticed I was still in 3rd gear. I had to re-train my brain a little bit - I didn't need to shift as often as I normally do because the power is extremely broad and each gear can be ridden lower and also revved out further. You can come into a corner a gear higher than normal, and it has plenty of torque to accelerate through the corner, and keep pulling down the straight."
 
But thats the beauty of this bike, its versatile enough to cater to sporty riding through mountain passes or sedate enough for multi state touring at a relaxed pace!!
 

[kemmotar]

SO,no need for a speedoDRD. (Speedo healer.) 
My FJ09 seems to be pretty optimistic on speed, a few MPH faster indicated than actual.
 
Anyone else have that same reading?
 
The only way to really change speed then is with tire diameter, or the speedoDRD.

Japanese bikes have always been relatively optimistic on speed. Some have been pretty awful, being off by as much as 8 or 9 mph. I think the FJ-09 is no more than about 2 or 3 mph off of what GPS indicates regardless of speed. What I mean is that it is 2 or 3 mph optimistic at 35 mph and still 2 or 3 mph optimistic at 85 mph. Compare that to some other bikes where the error in the speedo gets worse the faster you go. I consider the FJ-09 to be relatively accurate. Certainly its accurate enough for me. Probably good insurance for me in case a cop should point a radar gun at me.

 according to my tumer (he checked the denso oem ecu) the difference is aprox 7,5-8%.