Hi everyone, I am new to the board and have some questions.

I am the new owner of nikux's GS and I'd like to pick up where he left off.  I have a '99 gauge cluster with an '04 engine and I'd like to get the tachometer working again. I understand that the 04+ bikes have tachometers that are electronically coupled. I just can't seem to figure out how?

Do they read a signal off the crank? Camshaft? Am I able to replace just the tachometer for a newer unit?

Any help is appreciated. Thanks!

Well, the tach is driven by the ignitor unit. If you have a 99 bike with 99 wiring, there is no control from the ignitor box for the tach because it was mechanical back then.

I think you're sort of in a situation of sitting down on your hand with your middle finger extended and spinning until you're dizzy.

Someone might have a suggestion other than using an aftermarket speedo/tach.

Hmmmmmm that kinda makes me want to hook the oscilloscope to the line to the tach and see what it does. betcha I could make something to drive the electronic tach. Something to do this weekend in the cave.

Rats. I was looking for an easy way out.

Ok, so the newer bikes have coil packs which feed a signal to the tach. If that's the case, I'm assuming that the tach is just reading the impulse rather than something fancy like a PWM signal? This would make it easy to just buy a cheapo autometer gauge in ebay.

Quote from: h2lee on October 26, 2011, 04:51:58 PM
Rats. I was looking for an easy way out.

Why not just buy a tach from a pre '01 model?

Tach is driven by the ignition control unit (see wiring diagrams). No coil packs.
I don't know what that signal is until I look at it on the scope.
Since tach also has +12 going to it, it might just take in a string of pulses and calculates the RPM in the tach itself using some cheapie processor. Haven't ripped one open to see. Would like to, but don't have any junk ones to destroy.
Give me a few days to hook the trusty Tektronix up to that tach line on Suzi and I'll take a picture of the screen. There is supposed to be a way to download the scope data to the computer but I have to read the book my that famous Mexican author MANUAL to see how to do that.

or why not change out electrical harness and controls

Changing out harness involves changing the carbs to the newer ones. I'm assuming the older ones are on the engine.
Newer systems require the dual throttle cables, throttle position sensor, neutral switch that also indicates 1st and 2nd gears, and half of the connectors are different - so that means changing the handle bar controls, too.

Whole a harness can be had for $10-$20, the control box goes from $50-$100. Then the controls, carbs if they are not the newer ones with throttle position and some thing called a vacuum switch 

It might be easier to go aftermarket instruments.

Lets make a final determination after I see what the tach signal is. Might be pretty simple to get the right signal for the new tach. I have some signal generators. If I see what the signal is, and if I can make a signal generator work the tach, then I now I can make a new tack work on an old bike. I bet it's just a pulse train - not even PWM, just one pulse per spark of one cylinder. Now I really feel like doing it tonight after bowling. 

I have your solution, actually I posted the solution on here years ago.  searching on this site is largely hit or miss, depending on the keywords you use.

http://gstwins.com/gsboard/index.php?topic=39131.0
http://gstwins.com/gsboard/index.php?topic=16594.0

when I did the swap, I tapped the signal wire into a wire at the cdi box.  it worked great!

if you cant read and understand a wiring diagram, you're in for some heartache though.

Kinda what I figured would work, since going into the coil is 12 volt pulses.
Its late, so I'll wait until the weekend to play with the scope and run a signal generator into the tach.