Speedo shaft drive question

Not a lot but free to move a bit, if that helps.
There should be a shim washer either side so the shaft doesn't eat into the alloy housing.
 
Both washers are there. We're trying to found out, why speedos
do not show exact readings. Not across the whole range. Seem
to be oK at lower speeds.
Measured play is 1,6mm.

Ernesto
 
Sounds normal to me. That's the sort of free play I see.
The movement would 'wind up' when under load and then read constant.
If the needle is waving around then the needle damping is goosed and needs refilled with silicone fluid.
 
The problem is, it shows the speed exactly till arround 80-90 kmh, but above
this speed the tacho shows a lower speed than the bike has in real. ::)
The needle is not waving around.

As it is the second tacho we tried (both overholed), we thought it is something on the Speedo drive?
 
Only variable in the speedo drive is the tyre circumference.  This increases with increasing speed due to centrifugal forces and will thus "slow down" the speedo at high speed.  I seriously doubt that this will make a noticable difference at the speedo head, perhaps 2-3%.  If the experienced difference is too great in your opinion, try a different type of front tyre.

The magnetic drive of the instruments allows great tolerances and variancies in accuracy.  The person that "overhauled" the instrument should have asked for tyre size and circumference to properly calibrate the speedo, to at least attain an acceptable level of accuracy.  Very few magnetic drive instruments are 100% accurate across their entire range, something one just has to learn to live with. 

What's the difference between knowing you're doing 153.3 or 157.2km/h anyway? WTF does it matter? ::)

piet
 
What's the difference between knowing you're doing 153.3 or 157.2km/h anyway?
Click to expand...
Wouldn't even make up a thread for that, the deviation is much higher. I'm sure mr. superflute will present figures tomorrow.
So, Piet, how do you judge the play I mentioned (1,6mm)?
Anyway, when he's back on the road next month, I'll lend him my drive and wheel for a test.

Ernesto
 
Ernesto said:
Wouldn't even make up a thread for that, the deviation is much more. I'm sure mr. superflute will present figures tomorrow.
So, Piet, how do you judge the play I mentioned (1,6mm)?
Anyway, when he's back on the road next month, I'll lend him my drive and wheel for a test.

Ernesto
Click to expand...

Doesn't matter, has no influence at all.  Why should it?

I'd either check the threaded insert in which the gear is located for wear at the end, or simply add another washer if clearance seems excessive.  But it still has no effect at all on the drive of the speedo.

Have you checked the drive cable?  Have found quite a few in absolutely deplorable condition that only just managed to keep working.

piet
 
mr.superflute said:
The problem is, it shows the speed exactly till arround 80-90 kmh, but above
this speed the tacho shows a lower speed than the bike has in real. ::)
The needle is not waving around.

As it is the second tacho we tried (both overholed), we thought it is something on the Speedo drive?
Click to expand...
What size front tyre are you using ? cant see how the play in the drive would affect it really as if the gear will always be turning at the same speed as even if it floats it wont change the ratio
 
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