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Author Topic: Tachometer not working GT250R 2013  (Read 436 times)

jockwr

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Tachometer not working GT250R 2013
« on: December 26, 2018, 04:49:16 AM »

Hi,

I recently swapped out batteries in my bike.
After I had placed the new battery in, the tachometer did not work.
I took it for a ride to see if anything else was wrong, the speed, backlight, blinker/indicator lights etc are all working fine, it seems to be specifically the tachometer that is not working.

As you may be aware, when you turn the bike on (Without turning the engine on), the needle is supposed to go to the max rpm and then back to 0.
When I turn the bike on now, the needle moves a smidge and then goes back to 0. I've taken a video: https://www.youtube.com/watch?v=W94jDueeEIY&feature=youtu.be

If I rev the engine the needle goes up a smidge too.

I've read there is a cable under the seat which, if broken/disconnected can cause the tachometer to stop working.

Does anybody know which cable is the one. I don't want to play with all the cables and potentially break more.
Or if you have a different opinion on what could be wrong, please share.

Thanks.
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xuraax

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Re: Tachometer not working GT250R 2013
« Reply #1 on: December 26, 2018, 06:53:14 AM »

On my '13 GT250 bike I also suffered from erratic behaviour of the tacho unit. I traced the fault to a heavily corroded 4 pin connector just in front the tank which you can reach (with difficulty) from the right side. And this on a bike which is always garaged.

I replaced the connector with a proper water proof connector and so far the display is stable.

Good luck
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jockwr

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Re: Tachometer not working GT250R 2013
« Reply #2 on: December 26, 2018, 02:29:03 PM »

I had a quick look but didn't see any connectors there. I'll take the fairings off and take another look.

I turned the bike on with motor running and just started poking the cables located near the battery (No success). I did burn myself on one of the cables though. Any idea what these yellow cables are for? (Photos on google drive), sorry can't see any attachment options.
https://drive.google.com/open?id=1LiqbjomQRBhstUSBUVfBvrEEyNevAh1x
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umop-ǝpisdn

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Re: Tachometer not working GT250R 2013
« Reply #3 on: December 26, 2018, 09:52:15 PM »

Those three yellow wires are the three phases of the stator. They go to the regulator/rectifier.

The stator makes AC voltage in each of those phases and the reg/rec converts it to DC.

Voltage output by the stator climbs with RPM. At 5,000 RPM a healthy stator should be making about 60~70VAC between each of the three phases. What ever the voltage is, it should be roughly equal between the three phases. i.e. A -> B = 65VAC A -> C = 66VAC & B -> C = 65VAC, this is a healthy stator. ..but A -> C = 65VAC, A -> C = 30VAC and B -> C = 65VAC, this indicates a bad winding on the stator.

All three yellow wires are exactly the same, it doesn't matter which one you decide is A, B or C, so long as you stick with it through the testing.

DISCONNECT THE STATOR FROM THE REG/REC BEFORE TESTING.

..nothing bad would happen if you forgot, you just won't get an accurate reading. So, disconnect the hot plug, rev to 5,000 rpm and test voltage.

If the stator checks out as OK, then test your reg/rec.

The two jobs of the reg/rec are to regulate (limit output voltage to below 14.5V) and rectify, convert to DC.

It does this by merging the three AC phases from the stator into one DC phase. It 'dumps to ground' the excess. ..if the stator has a short circuit, then it tries to ground through the stator, which causes heat and loss of voltage. ...it is this that I suspect is happening.

FYI
A dead stator will very quickly kill a reg/rec.
A dead or dying reg/rec will eventually, over many months kill a stator.

Good luck!

Moral of the story. The earth wire coming out of the reg/rec matters A LOT. Without it, things get fscking hot.
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I used to be a sensitive, new age guy, but times have changed and now I am more of a caring, understanding, ninties type.

jockwr

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Re: Tachometer not working GT250R 2013
« Reply #4 on: December 27, 2018, 02:32:03 AM »

Fark, I can't disconnect the yellow cables, they seem to be bonded/melted together. There are a few black/burn marks on the connector.
Upon closer inspection, I can see the yellow insulation is splitting, exposing the wires (See photo here: https://drive.google.com/open?id=1TBkxaWeYgnQ79_G2GQkpZAurrKOh9LJz

I decided to test connectivity between the three pins/yellow cables with my multimeter. They all have 0 ohm resistance between each other (i.e. all connected together). Does that sound right to you?

If so, then I'll turn the bike on to heat the plug up and try to disconnect it once it's been heated.
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xuraax

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Re: Tachometer not working GT250R 2013
« Reply #5 on: December 27, 2018, 07:18:08 AM »

I had a quick look but didn't see any connectors there. I'll take the fairings off and take another look.

I have a Naked bike so of course I have no fairing there.

There are 2 or 3 connectors at the front very close to the steering column. If I remember well it was a white connector.

Once you find them it should be fairly easy to find which connector serves the Tacho.

With the ignition key off, disconnect one connector at a time and then turn on the key. The Tacho unit would be disabled but the fuel pump will still activate.
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umop-ǝpisdn

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Re: Tachometer not working GT250R 2013
« Reply #6 on: December 27, 2018, 09:18:16 AM »

I decided to test connectivity between the three pins/yellow cables with my multimeter. They all have 0 ohm resistance between each other (i.e. all connected together). Does that sound right to you?

Nope. You want 0.5 ~ 0.7 ohms between each pair., but again that assumes that you have disconnected the stator from the reg/rec.

Another, slightly more redneck way of checking is to smell your oil. If it has a burned smell then odds are you've got a bad stator.

Just to be clear here. You really don't even need to test the reg/rec. The only test you need to perform is to see if you can land it inside the bin from beside the bike, without standing up.

You're clarifying to see if the stator is bad or not, but there it no question here regarding the reg/rec. It's cactus.
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jockwr

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Re: Tachometer not working GT250R 2013
« Reply #7 on: December 27, 2018, 12:04:57 PM »

Quote
There are 2 or 3 connectors at the front very close to the steering column. If I remember well it was a white connector.

Once you find them it should be fairly easy to find which connector serves the Tacho.

With the ignition key off, disconnect one connector at a time and then turn on the key. The Tacho unit would be disabled but the fuel pump will still activate.

Ok thanks, I'll hopefully get to it tomorrow. Now i'm worried about the rectifier/stator issue fml.

Quote
You're clarifying to see if the stator is bad or not, but there it no question here regarding the reg/rec. It's cactus.

I managed to get the plugs apart, checks these out:
Plug that goes to rectifier: https://drive.google.com/open?id=1SnPgXPUJk8dx5ZiYwo1bMTYIGFqHfJOT
Plug that goes to stator: https://drive.google.com/open?id=1v9xqgsVWAI4hr_xN9mg5j4JVKOh6-GFG

Since the tacho isn't working, I can't check what's going on with the voltages at 5000 rpm.
Any chance I can check it at idle rpms? Do you have a reference voltage for idle?
I have measured the voltage after 5 minutes of idle, I'm getting 25v AC between all three pins (Reg/rec disconnected).

Another question: The five cables coming from the stator (3 yellow, 1 blue 1 green). What are the blue and green cables for?
« Last Edit: December 27, 2018, 01:11:51 PM by jockwr »
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jockwr

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Re: Tachometer not working GT250R 2013
« Reply #8 on: December 27, 2018, 01:47:58 PM »

Update on the stator voltage.
I revved the engine (blindly/no rpm readings) until I measured 60v across 2 of the pins coming off the stator. I then checked all combinations of the three yellow pins, all combinations gave about 60v +- a few volts probably due to slight release on the throttle.
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spit051261

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Re: Tachometer not working GT250R 2013
« Reply #9 on: December 27, 2018, 05:28:58 PM »

The other 2 wires are the Pick up coil I believe.
Your voltages look OK.
You need to see what voltage is coming out of the reg.
« Last Edit: December 27, 2018, 05:34:40 PM by spit051261 »
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