SV650S Speedometer Sensor Repair

[mw0cra]

I was wondering if anyone has had the same problem as me in that the electronic speed sensor on my SV650SK2 was not working even though the rotor was in good condition

Having priced up a replacement at £80 from ebay or £109 from a Suzuki dealer I decided to have a go at repairing it with some open heart surgery.

The main electronic component inside the encapsulated body was about £2 so I had nothing to lose.

To cut a long story short, it works a treat. Let me know if there is anyone out there who would like the details of the fix and I'll post it on here.

There may well be other bikes with a similar configuration that would benefit from the same treatment.

[kerby]

My K4 speedo packed up yesterday,rotors fine so next step is to test the sensor so please post up cheers

[Wofnutz]

Hi mw0cra,

I have the same problem with my speedo not working. I have not opened it up at all or checked the wires running to behind the radiator as I haven't had time to take off the tank to get under there. I also don't have a paddock stand, so haven't removed the front wheel to get at the rotor. If you can explain briefly what you did, it would be greatly appreciated. I wouldn't mind doing the open-heart surgery too as little parts like that shouldn't be in the region of £100...

Cheers,
Wofnutz
(2003 SV650S)

[Tim1200]

I would say post it matey

[mw0cra]

Finally put it on. Sorry, I didn't see the requests until recently



First of all I'll get the disclaimer out of the way.

The information I am giving is given in good faith with a view to saving you money as I did. I take no responsibility for any damage you cause in following these instructions. You do the tests or repairs entirely at your own risk. Some knowledge and practical experience of electronics is essential before attempting to repair the sensor.

Having bought an SV650SK2 with a speedometer not working, I followed the method of test in the repair manual to check if the sensor unit was working (with a slight modification to test it using 12Vdc supply rather than 6Vdc). The resistor is used because the output of the circuit is what is called ‘open collector’ and will not output a voltage on its own.

Picture 1 – Sensor Test Circuit

The rotor that spins with the front wheel is magnetised such that it has 4 north poles and 4 south poles. If working correctly the voltmeter reading should switch between 0V and supply voltage 4 times for each revolution of the wheel rotor.

From looking at forums, the rotor can be the cause of the problem. Damage can occur if not been positioned correctly when the front wheel is being refitted. Mine was in one piece and I used a small magnet to check for the attraction and repelling points around its circumference. The rotors are available for about £20 from a Suzuki dealer.

Having found that the sensor was faulty, a replacement on ebay was about £80 and from my local dealer £109 it left me no option but to try some ‘open heart surgery’ on the faulty unit.

The electronic part that senses the magnetic field of the rotor as it spins is known as a Hall Effect device and I found one that can do the job for under £2.

Using a small high speed cutting disc and grinding wheel, cut the old circuit out leaving just the plastic housing. Care must be taken as the potting compound used is very hard compared to the plastic of the housing. Also the plastic melts and sticks to the disc if you run it for too long at a time. The hole left is bit enough to fit the new circuit parts with ease. Note that the slots in the inside of the hole allow the potting compound to stay fixed in place so don’t cut too close to the edge.

Picture 2 – Gutted Housing

The original circuit uses surface mount components (a Hall Effect device and a small capacitor across the supply to reduce noise on the signal), but there is plenty of room to use through hole components and a small piece of strip board. I used 2 smaller capacitors connected in parallel to give a lower profile.
All the devices are available from good electronic suppliers such as RS, Farnell, CPC etc. Maplin don’t seem to have the Hall Effect device at the moment.

Actual construction of the board I built is shown in the pictures below.

Picture 3 – Sensor Circuit Board

The parts that I used on the board are:
1. Hall Effect Sensor (Honeywell SS411A)
2. Capacitor 100nF (2 x 50nF)
3. Small piece of strip board

Picture 4 – Actual Board Top and Bottom

Make sure that when you fit the board in place that the Hall Effect device is positioned close to where the rotor magnetic fields will pass.

Picture 5 – Board in Housing

Test the circuit to check it functions as described earlier. The wires can be attached and then the whole circuit board can then be potted to protect it from vibration and the weather.

Once the potting compound is cured, carefully fit the repaired speedometer sensor and rotor and repeat the test on the bike.

Fit the connector back to the loom of the bike and check to see if the Speedometer registers any speed. Note that spinning the front wheel by hand was not fast enough to register a speed but use of an electric drill on the tyre to spin it gave a speed of 10mph.

I hope that I have put enough detail in this for you to understand and hopefully you have a working speedometer again for much less than a complete replacement part.