Tachometer is inaccurate

741 Views 3 Replies 3 Participants Last post by Tamir, Apr 3, 2022

C0daBear1357

Discussion Starter · Apr 2, 2022

I recently changed out the backlight leds on my 2011 CBR250R (ABS). I had to pull apart the whole dash unit to get in there. This includes taking off the tachometer needle. The leds work great now but the needle is in the wrong position. For example, when I'm idling at a stop the tachometer reads 0. Also when I'm close to redline the needle is off by a few thousand rpms. Has anyone had this issue before and have an idea on how to align it properly?
Thanks in advance.

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Tamir

· #2 · Apr 2, 2022 (Edited)

C0daBear1357 said:
I recently changed out the backlight leds on my 2011 CBR250R (ABS). I had to pull apart the whole dash unit to get in there. This includes taking off the tachometer needle. The leds work great now but the needle is in the wrong position. For example, when I'm idling at a stop the tachometer reads 0. Also when I'm close to redline the needle is off by a few thousand rpms. Has anyone had this issue before and have an idea on how to align it properly?
Thanks in advance.

Updated
Hi
When you returning the needle to place, you should check that the rotary position of the speedometer stepper-motor shaft are aligned. I did not do it myself, but there is two videos at YouTube that demonstrates this action, and I attach it to you below (the first one starting at 8:00, the second starts at 17:22).
To fix the problem:
1. You need to repeat some of the disassembly operations, make yourself a cup of coffee, take a deep breath, work nicely slowly and patiently as you know how to work, and I believe it will be OK.
2. In the first video the needle connection is performed while the speedometer is connecting to external voltage source. In the second video it's a matter of guessing. You will connect voltage to be successful in the alignment-mission at the first time. BUT! To prevent a voltage connection to the wrong pin, and then possibly cause irreversible damage...temporary connect the connector at the back of the speedometer, and switch the main switch to the ON position (engine STOP switch OFF).
first one (starting at 8:00):

The second (starts at 17:22):

You will find one more video on the same subject in the list I made here: https://youtube.com/playlist?list=PLjksoAp4z0aAnAysAchOoVKN9vFa377kT

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DannoXYZ

· #3 · Apr 3, 2022

There's little bit of spring-preload to needle when it's sitting on stop, so you'll never be able get it back on shaft properly when engine's stopped. Here's how I was able to do it.

1. connect diagnostic tach to read actual RPM of engine (SUN make good unit
2. rev engine up to 2000rpm as shown on external tac
3. carefully re-install needle aimed at 2000pm

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Tamir

· #4 · Apr 3, 2022 (Edited)

DannoXYZ said:
There's little bit of spring-preload to needle when it's sitting on stop, so you'll never be able get it back on shaft properly when engine's stopped. Here's how I was able to do it.

1. connect diagnostic tach to read actual RPM of engine (SUN make good unit
2. rev engine up to 2000rpm as shown on external tac
3. carefully re-install needle aimed at 2000pm

No, there is no spring-preload mechanism, not even a mechanical stopper. I'm sure it's a stepper motor. How do you reset it? According to the videos, there are two options. And if already electrical equipment involved, then operate it as in the first video and that's it. Using an expensive external equipment, and adjusting while engine is working is unnecessary and overkill.
But thanks to your illuminating comment I re-edited my first comment

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