The CX 500 uses a cable driven tachometer from the camshaft to the tacho on the bar. This cable follows a circuitous route, and is a fairly common failure – however replacements are quite readily available.

With the popularity of Café style conversions of the CX500 series a lot of bikes are converted to electronic instruments that expect and electrical signal to drive the tacho input.

The short pulse time and high voltage of the CDI type ignition often is not compatible with these instruments inputs. Some work ok with the wire wound around the CDI spark lead, some will work ok with input connected to one of the stock timing pickups.

Many gauges just won’t work reliably using either of these connections.

The Rae-San Tacho Adaptor is a small and simple circuit that triggers from the high voltage spike of the CDI coil and drives a 12V swing out to the tachometer input – similar to the pulse the gauge would see from a TAI system – which is what they are generally designed to work with.

The Rae-San Tacho Adaptor performs a pulse stretch of the trigger pulse from the CDI coil to ensure that only a single pulse is generated for each spark plug fire and that the pulse is of the correct duration to ensure being detected by the gauge.

The Rae-San Tacho Adaptor is built using surface mount components to make it as small as possible and is sealed in glue lined heat shrink tubing to offer environmental protection. It’s small enough just to be tucked in with the wiring harness somewhere on the bike.


There are only 4 wires to deal with:

  • RED– switched power- goes to black on the bike harness
  • Green – Ground – goes to green in the bike harness or chassis
  • Yellow – Tacho output – this goes to your gauge tacho input.
  • White – CDI coil input – this goes to one of the CDI coil leads from the CDI module.


The Original CX 500 CDI stator (type G47) has a blue and white wire output that are used to generate high (200V+) voltage to power the original CDI system. This is the most common failure over time on these bikes and is responsible for the majority of the starting troubles and the dies at 4500 – 5500 Rpm behaviour.

If a new stator has been fitted, or it has been rewound – then leaving these high voltage connections open circuit and unused will quickly result in their failure again. If they are unloaded they generate higher voltages than normal and the insulation breaks down. If they are shorted together – they don’t generate the high voltage – but instead generate the maximum power they are capable of – and burn out after a while.

The configuration where they last longest – is when they are actually driving the ignition system - in the middle of their load range, with the voltage at normal levels.

The Rae-San dummy load is simply a circuit with a couple of capacitors, resistor and diodes that is designed to mimic the normal CDI ignition load.


You only need one if you can answer yes to all of the following:

  • Am I using an Ignitech or Rae-San ignition?
  • Are my Charging Coils (Blue + white wires (G47)) operational and producing the correct voltage?
  • Do I want to keep my charging coils operational?

If you wish to keep these coils alive then the addition of a dummy load will ensure your charging coils don’t fail due to over voltage or over power.


Plug it into the 2 pin connector with the blue and white wires. Blue -> Blue, White ->White.
Attach the Ground wire – Green to the chassis.

Done. Ride safe in the knowledge that you're CDI charging coils are not deteriorating further.

Please visit the Shop, to purchase Rae-San Accessories