Picked up a Sigma Targa bike computer on the weekend and fitted it to the GS.  If you can source the Sigma Targa model get it as it is designed for use in applications like Extreme Mountain bikes - hence has thicker cable (easier to splice) and the mounting bracket is rotated 90 degrees from the standard fitting - in my case made the mounting easier.

Fitting to the GS was easy, just ran the cable along the existing speedo cable and fitted the magnet to the plastic cover with the sensor on the fork.  The display unit is positioned above and between the two existing gauges (like Joris's mod) using a niffty little bracket I fabricated that srews onto the back of the gauge plate using the existing screw - looks quite tidy.  For the magnet I 1st tried one out of a fridge magnet gadget but it wasn't strong enough so in the end I used a magnet out of some airplane headphones.  Once I get my hands on a digital camera I will post some pictures.

One concern I do have is the effect of the magnet weight on the wheel.  I assume that given the fact it is mounted so close to the axle that it won't have any negative effects on wheel balance? (I am considering fitting a counter weight)

If you have a soldering iron, solder, shrink wrap, wire cutters, ally sheet metal and tin snips handy - this is one quick and easy mod to do.  All up cost was AU$50 (~US$39) as I had everthing bar the bike computer already.

Cheers
Conrad

Conrad,

Since I got hooked on cyclocomputers while on my bicycle, that item is on my shopping list.  I like the accuracy of the speedometer, but the clock and trip computers are just as handy.  The setups I've seen mount the magnet on the rear disc and the pickup on the swingarm.  I would like to see those pics!  I've only used Cateye computers on my bicycles, but their speedometers don't register at higher speeds.  My cycling catalogs don't show a Sigma "Targa" computer; only BC-xx00 alphanumerics.

You won't have a problem with wheel balance with your magnet, considering its low weight and its mounting location near the axle.

It will be another week or so before I get the digital camera (it belongs to work and is away with one of the employees).

The fitting was quite easy.  The steps below may help you and will support the pictures when I get them:

1. Fasten a magnet (I used a headphone voice coil magnet) to the platic cover on the left hand side of the wheel.  Make sure when the wheel spins the magnet doesn't hit the original speedo casing.  I at 1st tried some double-sided tape but that came off so final fitting was with some homemade ABS Glue/Putty (dissolved ABS plastic in MEK solution)

2. Cut the wire between the computer mounting bracket and the sensor.  I cut the wire closer to the computer mounting bracket so any joins will be as high as possible away from road grit and dirt.

3. Fix the sensor the the left hand fork leg.  My final fitting position was towards the front of the fork leg so there was a small gap between the magnet and the sensor.  I fixed the sensor using double-side tape and two zip ties.

4. Run the wire along the existing speedo cable, loosely wrapping it around the original speedo cable as you move up.  I used zip ties to secure the cable at even intervals.  This will run the bike computer cable up towards the GS's dash.

5. Fabricate the bracket to hold the computer's bracket.   The final piece looked like the image below.  If you look at the back of the GS's dash you will see a single screw between the two gauges.  This bracket fits behind the dash, between the two gauges and is fixed using this screw.

.______
.|-------|
.|-------|
.|-------|
..\--0--/
....\---/
.....|_|
.....|_|

6. Fit the computers bracket to the newly made and installed bracket using double-sided tape or any other method.

7. Run the wires from the computers bracket down along the original speedo cable.

8. Cut a piece of two core wire long enough to join up the wire from the sensor and the computer bracket.  Using a soldering iron and shrink tubing join the wires together.  Note when you cut the wires do the following to make life easier and prevent and shorts (xxx is where the two wires are soldered togeher)

------------xxx------
---xxx----------------

9. Fit the bike computer to its bracket, enter the correct time and front tire circumference

10. Ride and enjoy your new found speed accuracy.


Conrad

but what does it top out at?

Quote from: Blueknytbut what does it top out at?

The one I bought is rated to 300km/hr or 180mph!  Speaking to the couple who run the local bicycle shop, the Sigma computers are used by quite a few motorcyclist.  Most other bike computers only have 2 digits for speed whilst the Sigma has 3 digits.

Here another link http://www.st1100.org/farkles/sigma.html for an example on an install on a ST1100 using the Sigma BC-800.

Cheers
Conrad

Hey Blueknyt the 800 is a common mod for the KZ 400/440 guys. That yahoo group was full of those mods.
Cool.
Srinath.

Why do you need to cut the wiring harness?  If it is to short and you need to add to the length you can but the longer rear wheel harness for less than $8 US.

The Targa unit that you are using is no loger a curent model from Sigma or at least in the US market place but it is a very nice unit.

All of the new Sigma computers from the simple BC500 which retails around $20 US up to the BC1600 which shoulg go for around $30 US have a new mounting bracket design for the late 2003-04 models which allows for you to mount it in two different positions depending on the bicycle application.

I have been using Sigma Sport computer on my motorcycles for the last couple of years and have had no problems.

As for the fear of showing the correct speed this all depends on if the computer was set up with the correct tire size when installed.  If one enters the correct info into the computer then the speedo should be 99.9% correct.  Errors are due to not reading the instructions.

Quote from: tkm433Why do you need to cut the wiring harness?  If it is to short and you need to add to the length you can but the longer rear wheel harness for less than $8 US.

The Targa unit that you are using is no loger a curent model from Sigma or at least in the US market place but it is a very nice unit.

All of the new Sigma computers from the simple BC500 which retails around $20 US up to the BC1600 which shoulg go for around $30 US have a new mounting bracket design for the late 2003-04 models which allows for you to mount it in two different positions depending on the bicycle application.

I wanted the final wire length to be just right for the fit, the standard one was a bit short whilst the longer harness was too long.  If you can solder and use shrink wrap you end up with a reliable and neat finish (could have also used some quick crimp connectors if soldering isn't available).

I went for the Targa as it had the thicker cable - just more durable.  If you get a model with thinner cable you could look at fitting a protective sheath over the original cable - like a long length of shrink wrap.  It has all the features of the BC-800, the main ones I think that will last past the novelty phase will be trip distance, time, speed ---- it is interesting to be able to see your max and average speed after climbing a favourite mountain  

Cheers
Conrad

What do you guys have your wheel circumferance set at?

I'm sure the number varies depending on tire type, but all the values for a 110/70 tire should be pretty close.

I posted some pics of my similar install at http://www.gstwins.com/forum/viewtopic.php?p=40698#40698 .  Wish I would have known about the back-wheel pickup, as I went the cut-and-solder route also.

Sorry, I don't remember what my circumference is.  And it's probably different now that I've worn-down the tire.  I checked it by spitting on the tire then rolling the bike down the driveway and measuring the distances between the dots on the pavement; then I double-checked by using a measuring tape around the wheel.  If the circumference were 63 inches (wild-a$$-guess), then you should be able to get within 99.9% this way (within 1/10 inch).

But I've heard that your wheel will change more than 1% in circumference between cold/sitting in your driveway, to hot/spinning down the highway... that sounds plausible, and 1% would be like 1/2-inch of circumference!   I've heard that you can measure the wheel to get the approx. circumference, then go for some rides: ride at least 10 miles each time, and on several different highways.   If 3 highways agree how long a mile is, over a 10-mile stretch, then that's probably pretty accurate.

Unfortunately, this kind of precision is pointless unless you recallibrate every few thousand miles (to account for tire wear).  And if you ride 30 miles to recallibrate, you'd be spending 1% of your riding just  getting your speedo set.  So it's probably best to just measure the wheel once per season, and know that you're probably off by as much as 1mph.

Hello,
(sorry for the mistakes in words)

I picked up a Sigma Targa bike computer a day ago

and I would like to see pictures of yours motorcycles with Sigma...
I wondered where should I put every part of this computer?

Thx for helping me  :mrgreen:
@starte

Hmmm...
Anybody can help me  :dunno:
ja_00@op.pl
make some fotos of your bike and send me on my e-mail

Virtual beer for that...  


@starte

Just bought the cheapest Sigma BC last weekend and got it fitted today. I ended up zip-tieing the sensor to the left fork, and epoxying the included magnet to the plastic cover of the wheel.

Does anyone know an approximate diameter/circumference of the stock front wheel? Sadly enough I don't have so much as a tape measure to see for myself.

Thanks!

I bought a Acewell Digital Speedo , it does up to 180 mph also , Shift warning , Rev counter , etc

There really good , my acewell asks for the Wheel size , so i put in what the 17 inch is ,  and it worked fine ,
Really kool i think ,

Im looking to get a mini rev counterr so , i have it on a clock , just for when i need to get as close to that redline as possable