I was wondering around looking at parts last night on troy-racing.com. On the eletrical page Click here to see page I noticed there is a speed sensor. The yamaha manual says nothing about it, except on the sensor page it shows 3 wires, 1 ground and 2 that lead to the CDI box.

I wonder if one of these 2 wires grounds once a revolution, if so hooking up a speedo would be really easy, and it would be a direct connect into the yamaha wiring, no make shift mounting of sensors.

I would think this would be a speed sensor like I'm thinking about, no reason to do a RPM sensor, you already have that on the crank and can tell via the spark output.

Has anyone fooled with these wires or have any insight? Just asking before I go home and attempt to blow up a $300 cdi unit in testing

Brad

PS, the part I am wondering about is #14 5LP-83755-00-00 SENSOR, SPEED (U49)

 

Bueller??? Bueller??? Bueller???

Anyone have any knowledge at all on this..

Brad

 

I'm not sure about the sensors your talking about...But it would not be that simple. That sensor might be giving engine speed..Most likely in rpm's..how do you figure your going to do the calculation for actual speed...given different gearing and tiring sizes...etc?
It would be possible...your talking some coding...burning a chip....and creating the circuit.. But then your looking at a lot of development and work beyond most peoples knowledge.(unless you can buy or find a digital speedo with correction built in)

I would not risk trying to ground a wire that is connected to your cdi. Yamaha will not give out the internals of a cdi...so tracing a problem can be fun.

I would like to see the full wiring schematics for the bike.... I'm sure I could make a circuit that would be close. It would be the correction for the different variables I mentioned above that would be hard to do. (If a proper pulse can even be located somewhere on the bike.) Reading from the plug wires seems to me would be the most accurate.

 

Sayit...

I have figured this much out, the speed sensor is on the backside of the transmission. It has to be some type of true speed sensor, not an RPM sensor. I know for a fact the RPM is checked from the flywheel area.

From the location of the speed sensor I know it's somehow counting revs on the output side of the motor, hence past all the gearing so it'd be the same as checking it at the tires. Now I just have to figure out how it works.

If you want to see the sensor I am talking about look on the right side, right above the rear brake pedal. Go all the back to the back side of the case, then look for a sensor held in by a single allen head bolt. It will have 2 red/pinkish wires and one black with a white stripe. You'll notice the sensor sits right above the main output shaft, which has to spin in a direct relationship with the rear tires. (Notice I said direct relationship, not 1:1)

More to come..

Brad

 

Well..

Here is the scope.. or so says my fluke meter.

Black/white is ground.
Red is 12v+ while the engine is running (the key being on doesn't do it)
The pink wire is a pulse that could easily be converted to a true speedo.

It's hard to count high to lows with a fluke, but it appeared to be 12 pulses from ground to 5v high per revolution on the front (drive axle) sprocket. with a 3.07 gear ratio, that’s 36.84 pulses per tire revolution. I need to find a way to take every 36th pulse and output 1 pulse to the speedo.. from there I can adjust the speedo tire size enough to make it all work.

If the tires are 169cm in circumference, that’s 5.54 feet. 5280/5.54 = 953 revolutions per mile from the rear tires. Going 60 miles an hour you'd have 57180 rear tire revolutions per hour. That's 15.88 revs per second @ 60 miles per hour. The input side of the circuit from the drive axle would have to be able to read up to 571 (15.88*36= 571) pulses a second, while dividing it down by 36.

Any electronic majors in the house?

Anyone else follow my quick math and logic?

TIA
Brad

 

Have you tried looking up parts for the european street bike on the web? I am sure you are right about it being a speed sensor. Yamaha uses this motor in crotch rocket in Engaland, I saw the picture on the web somewhere one day. So the part to convert the signal or even an entire digital speedo that plugs into this sensor may already exist somewhere. Just something I remembered seeing so I thought I would share. Good luck with the speedo and keep us informed.

 

The European Yamaha is the SRZ 660. Most links I saw are not in english, but here's one.

http://www.supermono.co.uk/szr.htm

 

Jwrangler..

I haven't really looked at the european street bike, I bet you anything the speedo is an output from the CDI. Which would be different.

I have however designed a circuit to do whats needed.

The parts total, about $5.00 at rat shack. It uses 3 dual d type flip flops, a 5 volt regulator, and a board to solder it all to. I can then divide the signal down by either 32 or 64. While neither one of these is the needed 36, it ill be close enough to allow the catseye speedo to be calibrate with it's different tire size.

I am going to spend the time soldering up this circuit in the next couple days, I really want to have a speedo/odometer. This will be a very accurate one because it uses the factory sensor.

Total price including the CatsEye Speedo, under $35.00