Innacurate Speedo Reading

[nitro159]

Hi, I've got a basic chinese copy of a CG 125 and I recently worked out that my speedo is out by a good 10 Miles an Hour at speeds of 30 MPH and upwards, I checked this when I became frustrated with cars seemingly speeding away from me at all times, I put a GPS unit on my bike and rode around for about an hour at varying speeds and from just under 30MPH on the speedo, the GPS was reading 20 (give or take, seemed to fluctuate at that speed), When my speedo read 40, the GPS said 30 on the dot, and I was in harmony with the traffic! It did the same for 10MPH increments upwards to around 60 (scary) where the GPS read 60MPH but the speedo read just over 70.

Note the speedo is driven off of the front wheel, mechanical not a digital one.

Is there any way to adjust it myself without sending it off to a manufacturer or should I consider a new speedo? Any ideas or is this regular?

Also just before the pipe on the exhaust meets the bit where the exhaust widens toward the back, just underneath the back brake pedal, the exhaust appears to widen and appears to have had a piece of pipe welded between the downpipe and the part where it widens, the section is considerably noticeably wider in diameter and approximately 6 inches long.
Does anyone have any idea what this is because I haven't seen it on any other 125's.

Thank you in advance

Wayne

[Kickstart]

Hi

Probably not much you can do with the speedo to adjust it. Probably the easiest way to do it would be to put an overlay stickers on it with the real speeds.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[oldbiker]

All speedos are wrong and they are optimistic thats just the way they`r designed
____________________
It`s all powerfull white mans magic
https://i897.photobucket.com/albums/ac178/tzrsteve/album%201/035.jpg

[Pete.]

Not by 30%! If the error is repeatable then Keith's solution is the simplest. Fit an overlat sticker on the face of the clocks.

The wider piece of exhaust - dunno, could it be a catalytic converter, or another silencer in the pipe?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stirlinggaz]

hi,
ive found that most of the speedos on the chinky bikes i have had, have been inaccurate & a couple by as much as 20% +!
do what i do & fit a cheap bicycle computer. (the hard wired type)
very accurate, cheap & easy to fit.
(though you may have to improvise a bit, when fitting the magnets)
depending on the design of the magnets/fittings (make sure you can have a good look at it 1st before you buy as some of the magnets can be a pain to "stick" to the wheels- i have resorted to araldite before) & what type of wheels you have, it should be prettty much unoticeable.
cheers,
GAZ

[.]

A cycle speedo is not the cheapest option but certainly can be the most accurate.

I use a (discreet) £10 cycle speedo purchased from halfords and then used my (bulkier) GPS unit to calibrate it.
Had to purchase a neodymium magnet for £2 to get it to work correctly as the field strength of the standard magnet was not powerful enough to bridge the gap between the rim and the forks.

Even the cheap cycle units have the advantage of a trip meter and a clock.

[jokmm]

Hey there, you've got a similar bike to me then lol. I had this problem, but mine was under warranty so I got a new one put on. If it's the same as mine, it's basically a cable that is attached to the wheel and into the speedometer, and if this isn't rotating properly you'll get an incorrect reading. You could try disconnecting the cable and lubricating it, see if that helps. If not, replace the speedo drive.

Btw, what is your bike called?
____________________
If in doubt, give it a clout!
Current speed slave: Wuyang WY125

[nitro159]

Thanks for the quick replies guys! After a few more tests it can vary and i dont really want to rely on it for much longer, Im going to be getting a cycle computer and seeing what I can do with it, any ideas on the exhaust part?

@jokmm: Its a "Senke 125 - 4" Not sure what that'd mean compared to other chinese 125's.

Thanks again for all your help guys, very much appreciated!

Wayne

[MaybeGuy]

my chinese bike could do 100mph
____________________
Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[Martay]

100mph!? Is that it?!
My chinese 125 had an interesting feature. The speedo would show approx. 20mph while standing still, and the needle would hit the end stop under 0mph at anything above real 30mph. At a guess 155mph, but cant say for sure as the numbers stopped :p

Anyways, as has been said, an overlay on the clock. Or just put a small sticky dot or piece of label at genuine 30 + 70. They're the only speeds you really need to know. Dont spend too much on a cycle computer, i tried it, and killed it after 200ish miles.
____________________
Eat well, poo hard
Drives: Cavalier 2.0 16v
Rides: Slightly ratted Honda City Express

[stirlinggaz]

half decent (wired) bicycle speedos cost around a fiver

[Vincent]

I thought GPS speed indicators weren't accurate either Or are they just ok on flat straight roads

[Kickstart]

[Vincent]

OP, maybe the Chinese fit a slightly bigger radius tyre to go with the original Honda design speedo drive