Welcome to Otomotifan repair. How to check RPM meter if its, not working in your motorcycle or scooter. Rpm meters are basically two types mechanical and electrical now days, electrical type of RPM meter used widely the process i am going to show. You will be same for all brand of motorcycles and scooters. Let me first tell you about RPM meter wiring. If you understand that, then it will be easy to find out the problem.
I have open the back cover of meter case, so you can see the wires clearly. Rpm meter works mainly on tree wires. Color for these wires may vary in different brands, but working will be same black with yellow strip wire brings negative to the RPM meter. It connects with the negative terminal of the battery brown wire, brings the 12 volt supply to the RPM meter after the ignition key turn to on /start position or even after the motorcycle is started. The voltage generated by the magnet coil being regulated and supply throw this wire blue wire, also known as signal wire, which is connected to the positive of ignition coil.
Basically, this wire brings the pulsed dc voltage, which was supplied to the ignition coil from the CDI unit and finally helps to give reading through RPM meter about engine revolutions. If your RPM meter is not working, then, first of all, you need to check these three wires. If they working properly or not, you don’t have to open the meter case to check these wires. It can be done on the socket if you know the color code. If you don’t know the color code, i’ll show you how to find out which wire you need to check for what, whenever you’re checking any electrical component on the motorcycle make sure to check the volt of the battery set.
The multi-meter to 20 volt DC then connect the probes to the battery and reading should be above 12 volts due to poor connection of probes. Voltage fluctuates otherwise. The volt is above 12 volt. You can know the color of negative and positive wire from ignition switch socket. There are mainly four wires one wire directly connected to battery positive (, white, ) and, and one have negative black/yellow.
There will be another wire which will have 12 volt after we turn the key to on/start position. In my case, its brown and this brown wire will take 12 volt supply to RPM meter. So this is the simple way to know the color code of positive and negative from ignition socket. I turn the key to ON position and know we should have 12 volt supply on the brown wire. First, we check your negative wire for that set the multi-meter to continuity, then one probe to black/yellow, wire and other to body.
As soon as i touch the other probe to body ground, it shows reading that means this wire have negative to it. Now we set the multi-meter to 20 dc volt and check the voltage on the brown wire connect, one probe to brown wire and other to body ground, and we should have 12 volt. This prove that wire is in good shape and if, in your case, there is no reading, then wire must be cut some. Where now we check the third wire plus, if you don’t know, the color, then easy way to find out is look at the ignition coil. Look for the wire to the first ignition coils and you will see 3 wire, one will be -ve, one will be connected to CDi and the 3rd one will be the signal wire.
As you can see, this positive wire is black, and the signal wire to the RPM meter is black too. To check this wire, we perform a continuity test and for that set the multi-meter to continuity. If the wires of multi-meter are small, then use a extra piece of wire to perform. This test connect one probe of multi-meter to 1st ignition, coil, positive and other wire to black color wire on the socket. As soon as i touch the probe, there is beep sound plus reading.
That means the wire is good. If you don’t get the continuity in this wire, then that means it got cut near the handle and you need to repair it to be further sure. You can connect a wire piece to the ignition coil positive to direct RPM meter single wire. Then start the motorcycle and if the RPM meter still not show anything, then the RPM meter is bad and if the RPM meter show some reading, then there must be fault in the wire and you need to repair it. Let me show you if my RPM meter works or not plus i’ll, show you what happen if RPM meter not get 12 volt supply.
According to all the checks we done, my RPM meter should work and its working quit good. Now i’ll cut the 12 volt supply from battery and my magnet coil is faulty and does’t produce any volt. Now the RPM meter will not get any volt supply and it will not work like it was working before. As you can see the difference, the RPM meter is not working because its not getting any 12 voltage supply and if i connect the battery again, the RPM meter start showing reading again, because RPM meter gets 12 volt again. This is how you can check you RPM meter, for problems if its not working.