TACH

[KRB]

Have a 1998 Yamaha prov 200 carburetor model and tach stopped working. Can anyone tell me where the signal comes from. I have power to a new tach. Tach powers up and drops to o but that is it. Can the regulator cause the problem ? I checked continuity from the green wire out of the bottom of the CPU and it reads like 1.2. So there is no broken line. Should I replace the regulator ? From what I have read the signal come off the charging coil (lighting coil) to the regulator and then I assume it goes to the CPU, then out to the tack. Mechanic said he was able to connect to the green wires off the charging coil that go into the regulator to or jump to the green wire that comes out of the CPU and the tach worked. Any ideas ?

[Bass Junkie]

I'm chime in here since no one else has but I wouldn't consider myself to be an expert on the matter. Signal comes from rectifier. If the rectifier was bad I think you would more than likely see a high or erratic reading on the tach. The rectifier regulates the electrical impulse coming from the stator, which is the charging system. When it goes bad you get a high voltage coming out of it, in a lot of cases, and thus a high reading on the tach because the tach is voltage sensitive. When the motor is running how much voltage is reading at the battery and/or you dash mounted volt meter?

[yam911]

In a P200 the tachometer signal comes from the CDI. The green wire.

Is their continuity on the green wire at its terminal that connets to the CDI all the way to the green wire at the tachometer? There are several connectors along the way that can be defective, not allowing the tachometer signal to get to the tachometer.

The tachometer is looking for frequency on the green wire. Not voltage.

[KRB]

Yes have continuity from CDI connection to the back of the tachometer. Resistance reads 1.2. Is that to high to get signal through. Line is not broken. Not sure what reading is needed for frequency to get through. Mechanic said he jumped a wire from the 3 green wires into the rectifier to the green wire out of the CDI and it worked. You ever heard of that ?

[yam911]

Yes have continuity from CDI connection to the back of the tachometer. Resistance reads 1.2. Is that to high to get signal through. Line is not broken. Not sure what reading is needed for frequency to get through. Mechanic said he jumped a wire from the 3 green wires into the rectifier to the green wire out of the CDI and it worked. You ever heard of that ?

Some Yams use AC voltage from the lighting coil to drive a tachometer. Some Yams use DC voltage from a R/R to drive a tachometer. While it may work (what your mechanic did) did it display the correct RPM?

A cheap meter that displays frequency can be used to determine if the frequency is being made available to the tachometer. Connect the frequency meter to the green wire. Run the motor. Measure the frequency. On some Yams you will see 10 Hz for each 100 RPM.

https://vimeo.com/283175157

Do you have a spare unused wall wart around? A 120 volt AC to 12 volt DC converter? It can be used to see if a tachometer is working.

[KRB]

Since some us rectifier do you think that could be it since the mechanic essentially just bypassed the rectifier to the green wire out of the CDI. The signal coming off of the lighting coil and into the rectifier. Does it then go through the CDI and out the green wire ? If so sounds like it could be the rectifier maybe.