I think properly. For me strange what odometer works fine.
Not strange at all. The odometer works counting rotations. Does not care about speed. Check the cable as told above. It's either that or a damaged speedometer. My bet is on the cable though.
You can detach the end from the wheel side and check if it rotates smoothly by hand.
Mito57 is entirely correct. In effect, the speedo and odo are just 2 separate instruments housed in the same case. The odo is mechanically
connected to your front wheel. The speedo is magnetically
connected to your front wheel. The best advice has already been given: Remove, clean and lubricate the speedo cable. Do it right straight up.
1. Remove the entire speedo cable - inner and outer.
2. Use solvent (petrol will be fine) to clean out the outer cable and also thoroughly
wash/degrease the inner cable. You want both to be completely
clean and degreased.
smear any garden variety automotive grease all over the inner cable.
You don't want heaps of big dags of grease - a light smear along the entire length.
4. Put it all back together and test run it.
Chances are it'll be fixed. If not, 99.837% chance it's in the speedo mechanism itself. Not considered repairable! Most (the vast, VAST majority) are cheap, crappy, mass-produced pieces of junk for which no parts or service/calibration instructions are available. Even when I was working in my trade (Scientific Instrument Maker and Repairer), where I had calibration equipment, I only tried a couple of times before I decided that replacement was the only real option. Working on them is entirely a hit and miss affair.
If that's the case get an aftermarket alternative (Vapour, Koso, Acewell, etc) which you can calibrate to a high degree of accuracy without the need for professional help. Also, without the need for a speedo cable - always a bonus!topic19628-50.html
Look at the top of page 6.