Topic: Speedometer off

[thelowmax]

I haven't been able to confirm this with exact numbers but I'm pretty sure my speedometer is off. I will be in rush hour traffic and my speedometer will read that I am going 90+MPH, when I know I can't be going much more than 70+. There's no way the entire pack of daily commuters is blasting through town at 90+. How can I get exact measurements? Is there a way to adjust the speedo? What would cause my speedo to read so off?

[kghost]

Where did you get the speedo?

The speedos go with the drive and are specific to model.

right speedo with a wrong drive = off as does wrong speedo with right drive.

Their often the same shape and size lol.

[Duanob]

A couple of reasons why speedos can be off. Speedo from a different bike? Different size tire from stock?

[thelowmax]

This is on my CB750k8. The front tire is the stock 19". I think the speedo was stock too but I may be wrong. The gauges look right for the 78. How can I tell? Would the speedo from an earlier SOHC throw it off that much?

Anybody have a simple way to measure speedo accuracy?

[kghost]

Anybody have a simple way to measure speedo accuracy?

GPS, a timed mile. or a pace vehicle will all work.

A picture of the speedo would probably speed identification

[750K]

Find a newer Honda civic and ride beside the drivers door, they have a big digital looking speedo you can easily see from a car or bike plus they're everywhere. At least in my area they're everywhere you look.

[ekpent]

I always like to check my speedo with those large digital speed trap type mobile warning signs they set up around here sometimes in various places. On our interstate every mile is marked with a sign mile marker number. Do a mile with the markers at 60 and time yourself, should be 60 seconds, if the cagers don't kill you going that slow 

[Black 750K8]

My local police don't mind helping they get up to the speed limit 60mph then light me up to let me know to check my speedometer. There speedometers on calibrated every year. Just look for one in a parking lot and ask. If you think about it there speedometers are the only ones that count. All of our speedometers are off a little. Mine is about 6mph at 60 it reads about 66.

[bjatwood]

My K3's is off at speed too. You can also check the speed with a free speedometer app for your smartphone. It positions you via GPS, very cool app IMO..

[Dream750]

My K3's is off at speed too. You can also check the speed with a free speedometer app for your smartphone. It positions you via GPS, very cool app IMO..

What BJ said. 

I use the android (free app) Speed View GPS speedometer and it comes with the handy 0-60 and 1/4 mile feature.

http://www.appbrain.com/app/speedview%3A-gps-speedometer/com.codesector.speedview.free

(there is also a Speed View Pro version available for purchase, but I haven't tried it) 

[Bodi]

I don't think there's any excellent way to tell if your speedo is the correct model. I've looked at a lot of them at swap meets and beyond the size and where the trip reset knob, lamp sockets, and cable fitting are - I don't know how to identify the model it's for. The SOHC4 speedos all look roughly the same, and Honda uses different speedo ratios for bikes under/over 500cc. I can't recall them at the moment but the amount yours is reading high suggests you have the wrong one.
To check whether it's the wrong speedo or the reading is just whacky, ride a measured mile and see what the odometer tells you. The odometer drive is directly off the cable drive, and will be accurate as far as miles/wheel rev (at the particular ratio of your speedo). The MPH needle drives through a magnetic clutch system that is not so accurate. If you get close to a mile increment on the odometer over a measured mile, the speedo type is correct but the needle reading is high. If you read way more than a mile distance then you likely have a speedo for a sub-500cc bike.

[thelowmax]

I'm going to try the app.

[andy750]

App or a dedicated GPS unit. On my CB750K2 or K4 the speedo is off by ~4-5 mph up to 100 mph.



cheers
Andy

[DJ_AX]

Commuters around Detroit go 90+mph ... either that or 24mph.

Yeah I just strapped (lots of electrical tape) my phone to my handlebars w/ a GPS running...

I've found MOST speedometers are off...

My 750 ... is right on.
The 550 ... reads about 9% too high
The 350G ... 5% too high.
My wifes 2007 Chevy... reads maybe 2% too high.
My 2002 Huyndai ... reads 5% too high.
One car I drove was just over 10% too high.
I'd say about half of the vehicles I've driven are really close.
The other half usually reads about 5% high.

FWIW

[thelowmax]

I just got some Velcro straps and a sponge for a pad. Hopefully it will hold. I mean, what good is a free app if you break your phone using it. Wish me luck.

[Mooshie]

I had an aftermarket speedo that brand new was off by about 10% (got up to 10% in higher ranges--low speed was off by about 5%).  Then on my last trip it was off by 20% almost all the time.  Basically that meant the speedo was going bad (remember it was not stock).  So purchased a new one (better quality) and now it runs off at about 5-7% at higher ranges--low speed dead on). 
That was my experience anyway, may not be yours.

[thelowmax]

So, I downloaded an app call SpeedHud.  All it is is a blue or black screen with BIG number in opposite Blue or Black. I've tried it in my car and it works great and is easy to see. Then I bought a iPhone case that straps to my wrist like a watch. Now all I have to do is wait for the snow to go away.

[strynboen]

mine are +10 at 100 kmt..think to pull the needel..and put it 10 back from start..just for a test