XJ650 electronic rev counter

XJ650 4KO or SECA
Hi, Is there any way of fixing electronic tachometers ? I have voltage going to it but when I rev the engine it might go up to 2k revs max. It doesn't register anything when ticking over. I tried to upload a video but had major problems unfortunately. Doesn't seem to be any way to open the rev counter. Is it just a case of trying to find a good secondhand one, hard to come by over here. Thanks

 

I remember that my 83 650 Maxim had some issues with the tach. Mine just didn't like working if the sun hadnt been beating on it forna couple hours.

 

Unfortunately this is Ireland, who knows if the sun will shine here in 2023 !

 

The Maxim style gauges can be easily disassembled for repair, the SECA style (round with a metal crimp ring) are more time consuming and delicate to open up. Definitely not the easiest gauge to find. There are companies that repair gauges, not sure what your budget is for that or availability in your area.

 

You can open it yourself…….it’s the same procedure as for the 700 gauges….

http://www.xj4ever.com/repairing your 700 gauges.pdf

 

Thanks very much everyone for the replies and info. I don't know of anyone on the island that can fix these things. I have found second hand rev counter in France, cost about €130/$140. I suppose I have nothing to lose by trying to take it apart and see if internal workings can be loosened up.

 

Tacho not meant to be opened really but quite easy to do, just gently ease back metal ring and open two small nuts on back of case that hold gauge and workings in place. For anyone interested in seeing what is inside an XJ650 electronic tacho, photos attached. It is really clean inside but looks like no user serviceable parts.

 

Looks like the medium and large capacitors are not blown. Don't see resisters blackened or cracked. The black diode, can't really see. Those are all serviceable parts.

 

You can test the meter movement by disconnecting the red and black wires at the spade connectors and connect them to a 1.5 volt battery. The meter should read approximately 5K to 7.5K if it is similar to other Yamaha tachometers, which are scaled at approximately .2 to .3V per 1000 RPM

If it moves smoothly and returns OK then the issue is either the board or the wiring on the bike harness. It's a pretty simple board that converts frequency to DC, but to check it out of the bike you would need a signal generator or some other creative way to apply a pulse

 

Again, thanks for the info. I'm definitely not an electrician or Instrument Tech but have a very basic understanding of electrics. I tried connecting a 1.5v battery to Black and Orange (Red) wires with Brown connected to 12v on bike but no movement. The strange thing is that if I connect the tacho and rev the bike up to what I would think is 5-6k revs then the tacho goes up to 1k revs. Huntchuks, I have attached a couple of photos of black diode ? I'm making enquiries locally to see if there are any other XJ's in the area. It would answer a lot of questions if I could try my tacho on their bike or their tacho on my bike.

 

You need to unhook the black and red wires shown below to test the movement. You can disconnect by pulling gently on them. No need to hook the tach up to the bike, you can bench test. The needle should swing up, if it tries to go counterclockwise just reverse the polarity (switch the battery around). If the needle moves accordingly then the movement is good and the issue lies with something on the board or bike (unlikely if you are getting some movement and it runs properly).

 

Aah. Thanks for the image. I tried it with a 1.5v battery and nothing. I had an old 9v battery and thought what the hell, connected it and needle went to 1500rpm approx. The needle moves freely when pushed by hand and the mechanism inside (electromagnet?) is also free moving. To me the above would suggest that the rev counter is the problem, I appreciate everyone's assistance, great forum.

 

What looked like a black diode was on the other side. Many components can be checked with a meter but results for some may vary while still attached to the board. Look up the color coding for the resisters before checking those.

 

Yea the 9 volts should peg the meter - not good for it if working. That said, it is an electromagnet working in conjunction with permanent magnets that make the meter move. It should ohm out to around 75 ohms, but if it doesn't and is quite high (thinking it will be) there is not much you can do because the connection to the electromagnet is through the meter movement springs and is extremely delicate.