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Sigma Cyclometer Installation
System Category: Controls
Activity Type: Accessory
FJR Model Year: 2003  2004  2004 ABS  All model years
Author:Warchild
Date Submitted:Oct, 2003
 

Sigma Cyclometer Installation

The Yamaha FJR1300 has a surprisingly accurate speedometer, certainly compared with the likes of Honda, et al, bikes that are notorious for outrageously optimistic speedometers, often reading 7-9% high. Installing a Sigma cyclometer allows one to enjoy a deadly accurate speedometer/odometer. One that, when calibrated correctly, has virtually GPS-like accuracy up to 183 mph! Not that you would ever want to exceed the posted speed limit, of course.

However, if you did, you could do so with complete accuracy.

Why a Cyclometer?

The Sigma family of cyclometers was originally designed for bicyle roadracing/training use, but has a multitude of features that make it a worthwhile farkle for your FJR or any motorcycle, such as:

  • Playing Time/Distance/Fuel games while underway

  • Provides a backup to your main speedometer/odometer system

  • Using the Sigma for timing purposes on your favorite canyon run (!)
Sigma Cyclometer features
1. KMH / MPH
2. TRP
3. CLK
4. STP
5. MAX
6. AVS
7. + • -
8. WS
9. DST 1 / DST 2
10. TOTDST
11. TOT
  speed readout up to 183 mph / 300 kmh
trip distance
clock - 12hr ( mph) / 24 hr (kmh)
riding time - auto start/stop
maximum speed since last reset
average rolling speed
comparison - actual / average speed
2 wheel sizes programmable
2 odometer logs - each up to 99,999 mi.
total riding distance, DST 1 + DST 2
total riding time, aggregate stopwatch

Installing a Sigma has been a routine farkle among the Long Distance community for many years. Endurance rallies are all about time/distance/fuel management, thus the Sigma is an excellent and extremely useful weapon in the Endurance Rider's arsenal. And unlike a GPS unit, the Iron Butt Association allows the use of a Sigma cyclometer as a legitimate substitute for the bike's factory speedo/odo.

How it works:

The Sigma system is comprised of three main components: the head display unit (which houses the computer), a magnetic sensor, and a small magnet. The magnet is mounted somewhere on the rotating wheel, and the sensor is mounted in such as way that allows the magnet to pass close by the sensor as the wheel rotates. When it does, the sensor sends a signal to the computer to indicate the wheel has made one revolution. The computer then calculates the time it took for this one wheel rotation to occur, and compares it with the previous wheel rotation time. Using a formula based upon wheel diameter and time differences in wheel rotation, the computer can then calculate and display the prevailing speed with tremendous accuracy.

Below is cockpit-view of the Sigma BC1200 that mounted near the FJR's brake reservoir:
Sigma BC1200
The main challenge in this farkle rests with designing and fabricating an appropriate bracket for the magnet sensor. A magnet must of course be somehow affixed to some portion of the wheel such that it passes within close proximity to the sensor in order to trip the sensor and have it send data to the main unit with every wheel rotation.

Fortunately in the case of the ABS model, the rear ABS sensor bracket jumps out as a splendid mounting opportunity for the Sigma sensor bracket, with it's small horizontal shelf adjacent the rotating wheel accompanied by a nearby allen-head fastener. And we see the rotor carrier bolt head would nicely house a small rare earth magnet. This then, looks to need a bracket with two 90-degree bends, and a hole drilled in the end for the existing ABS sensor bracket bolt to pass through::

Sigma sensor mounting opportunity

So we draw a 55mm x 12mm strip on a piece of aluminum, and drill the mounting hole:
And after two 90-degree bends in the bracket, we try an initial fitting... looking good!

OK, now we dial in the Sigma sensor, zip-tie it in place. Yellow arrow points to rotor carrier bolt head that has a small rare-earth magnet glued within. Magnet passes within 2mm of sensor body to ensure positive signaling:

Here we start the long process of stringing the wire circuit up the chassis. The ABS circuit line is not only used as a guide, it serves as zip-tie mounts as the Sigma circuit is routed forward (denoted by cyan line below):

Because the circuit (denoted by cyan line) is routed through the hot engine bay, it is encased in that excellent NAPA heat-resistant "asphalt" wire loom to protect it from meltdown:

Notes:

  • After the circuit is routed to the handlebars, connect to the head unit, and calibrate the unit according to the instructions provided.
  • While I happen to use an older BC1200 model in the photos above, the most current model as of this writing is the Sigma BC 1600. The Sigma BC series of cyclometers can be found in any reputable bicycle shop, or mail order. Sigma's web site: http://www.sigmasport.com/index_usa.html
  • Small rare-earth magnets can be found at Radio Shack, known as "Rare-Earth Super Magnets" Catalog #: 64-1895, for less than $2.00
  • If you have access to one, endeavor to use a GPS to compare/fine-tune the Sigma. This will allow you to calibrate the Sigma to a high degree of accuracy.
  • If you have a non-ABS model, you will of course not be able to use the exact same bracket mounting method that I used here; you'll have to devise your own bracket.

 


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