Honda CBR 125 (2012-onwards) Digital speedo is erratic

Sub_Steppa367 · L Plate Warrior Joined: 30 Dec 2018 Karma :

I purchased my first motorbike today, it's a used a honda CBR125 2012 model. After about 30 miles of riding the speedometer started jumping up and down and showing speeds between 0 - 150mph, i was travelling at about 30mph. There are no other obvious issues to comment on. After a further 5 or so miles it self corrected and began showing what i would estimate to be the correct speed. Restarting the bike doesn't affect it.

Do you know what might be causing this and if it's something a novice would be able to fix at home? I haven't been able to find a solution to this problem online and was hoping someone would be able to help me, otherwise it's a trip to the shop. Thanks!

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Has this bike a warranty?
Many years ago a mechanical cable ran from the front wheel to the speedo clock, yours could have an electrical cable??
I would check the cable and connections first then check the sensor for being clean.

Sub_Steppa367 · L Plate Warrior Joined: 30 Dec 2018 Karma :

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

That's the symptoms you typically see just before the cable snaps.
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bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

visit cmsnl and find your bike. I could not find a 2012 model so looked at the 2011 uk one.

It has an electronic speedo with a dog driven sensor at the wheel, very similar to a cable driven type, but not identical.

A dog drive plate is there which, if the wheel is not correctly fitted etc. can bend the dogs on the dog rive plate.

This could cause this problem as well as damage the actual sensor, but your suggests a bad connection in the system.

Does the neutral light misbeahave, or any other lights misbehave when the handle bars are turned from lock to lock??

The wire from the sensor up to the instruments has to flex due to the suspension movement, an ideal fatique and make and break bad connection, so test that as well.
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Sub_Steppa367 · L Plate Warrior Joined: 30 Dec 2018 Karma :

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

Post a wiring diagram for this bike which will show how many wires go to the sensor, 2 or 3??

cmsnl does not show whats inside the sensor, may be similar to ABS type sensor ( both types ) . Post some pics of the sensor and what the dog plate drives. As said if the wheel has been fitted poorly, the dog plate dogs may be "bent".
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