Honda CBR650F speedo inaccurate

[MotorBike001]

Recently, I took the bike from the Midlands to Wales, and the Mrs took the car.  A few times I was behind her and she seemed to be going 85/90 mph.  But, later she said she didn't got over 75 (she is a know liar though :)).

 

This led me to think that my speedo is inaccurate.  Sometimes on the motorway I could be doing 90mph and a car flies past me - possibly 20/30mph more than me.

 

The bike had the MOT this morning, and I asked about the speedo.  They said the official line is it can be +/- 10% plus 6.25mph, and they don't know any way of checking that my speedo is way off.

 

Has anyone else had similar issues and got them sorted?

[Mississippi Bullfrog]

Can you check it against a sat nav?

 

I was on the motorway yesterday doing an indicated 75mph which I know is really just under 70. I was the slowest thing on the road. Motorway speed limits are ignored by most people.

 

 

[MotorBike001]

1 hour ago, Mississippi Bullfrog said:

Can you check it against a sat nav?

 

I was on the motorway yesterday doing an indicated 75mph which I know is really just under 70. I was the slowest thing on the road. Motorway speed limits are ignored by most people.

 

 

Umm - not really.  I don't have a phone holder on the bike (for GPS I use earphones with my phone in my pocket).

 

I suppose I could test it with the Mrs - ask/tell her to drive at 70mph and see what my speedo indicates.  Don't know if I'll get round to that though.

 

I just wondered if it's common for speedo's to become inaccurate over time.  I'm not quite sure how they work - if they're linked to the wheel, or the engine/gearing  mechanism.

[dynax]

Check it against one of them speed signs, but the majority of speedo's are out anyway I don't think I have ever had one that showed the correct speed

[Ian Frog]

ALL speedos are inaccurate !

Firstly no manufacturer wants to be called to court by someone who was done for speeding who then goes on to try to prove the manufacturer caused their problem.

Secondly when testing against radar equipment at Elvington as far as we could tell speedos were all approx 10% out always reading under ! Small test sample but the big four bike manufacturers represented along with BMW cars Audis and a motley selection of vans all available one speed weekend from the paddock.

Cheers

Ian

[Yorky]

2 hours ago, Ian Frog said:

 always reading under !

 

Are you sure you've got that the right way around ??

[Steve_M]

Both my bike and car are about 5% optimistic checked against my satnav. 
 

I had my riding assessed by a copper on a police bike. I was on my VFR and he used VASCAR to check my speed on a dual carriageway. My VFR is, according to that check, 10% optimistic. He asked me to ride at an indicated 75mph with him following… I found that a challenge with a fully dressed police bike following me.

[Stu]

Changed the gearing on the bike? that will affect it 

 

You could probably find an app for your phone that would track your speed and log it so you could easily set your speed at say 80 on the motorway for a set distance then stop at services and check the app 

[Ian Frog]

11 hours ago, Yorky said:

 

Are you sure you've got that the right way around ??

You are right ! My bad should have said reading over lol.

Cheers

Ian

[dynax]

Get a gps speedometer

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=gps+speedometer&_sacat=0

[MotorBike001]

12 hours ago, Stu said:

Changed the gearing on the bike? that will affect it 

 

You could probably find an app for your phone that would track your speed and log it so you could easily set your speed at say 80 on the motorway for a set distance then stop at services and check the app 

I haven't changed any gearing - the bike is factory standard.

 

I'll give that a go - I do use Geo Tracker and think that shows maximum speed over a trip.. 

[JRH]

Compared to my SatNav the Speedo was about 7 mph out at 70. Reading faster of course.

Speedo is off the front sprocket. Rear tyre wear also makes a difference.

 

[Bender]

Cable tie the phone somewhere temp and use GPS on that

[jedibiker]

I just got a speedo app and had phone on the bars, even if you get a cheap phone holder to test then bin it. ive got an old one you can have for postage if needed.

tested mine and its 5mph out til about 80 then the gap is a bit bigger.

[fullscreenaging]

It could be the speed sensor on its way out. 
Mine went on my 2002 CBR600F. 
Cost a bloody fortune to get sorted as I wasn’t confident in doing it myself. 
 

[MotorBike001]

So I cable-tied my phone to my handlebars and tested the accuracy of the speedo against my phone (using Google Maps speed).

 

The results indicate that the bike speedo is 9-12% above the actual speed (assuming the phone is accurate).   

 

Thanks for your help guys