3C speedometer reading very slow.

J

JezB

New member
Location
Scarborough
First ride out - it's reading 20 when doing about 35 - 40. Suggestions please. could be a cable problem - don't know. It's too cold to be messing in the garage this aft!
 
Did you omit it was wavering between correct reading and the speed you ought to be going at, naughty, must not ride 3c too fast, your mother will tell you so...j.
 
I experienced an erratic speedo reading that got worse over time. At times slow, then erratic becoming more common until eventually it didn’t work most of the time. Problem was wear of cable at wheel gearbox end. New cable sorted it out. My findings were cable end which should be of square section had rounded. My bike is a series 2 running ND instruments. Has yours always read slow or only recently? Could be instrument itself, perhaps test by driving cable using a drill rotating in the right direction attached to wheel end. Could even be an inner cable that is too short for outer sleeve, inner will ride up into the instrument potentially becoming disengaged at the gearbox shaft which is crimped locally to form a square section to drive the cable. Inner cable should have a ‚ferrule’ at speedo end that prevents inner dropping too far through outer and into the wheel gearbox so disengaging at instrument and conversely ride up into the instrument so potentially disengaging at wheel gearbox. Is this ferrule fitted and secure? If buying a new cable check that the dia of the new inner is similar to that of existing. The first new cable that I bought was of smaller diameter, hence the formed square ends were not optimal and cable wouldn’t drive the Speedo. Took a while to get that resolved.
 
Another common one is the worm and ring gears wearing out so 'slippage' occurs, gradually worsening until the ring gear no longer engages and the speedo reads zero.
 
laverda180 said:
I experienced an erratic speedo reading that got worse over time. At times slow, then erratic becoming more common until eventually it didn’t work most of the time. Problem was wear of cable at wheel gearbox end. New cable sorted it out. My findings were cable end which should be of square section had rounded. My bike is a series 2 running ND instruments. Has yours always read slow or only recently? Could be instrument itself, perhaps test by driving cable using a drill rotating in the right direction attached to wheel end. Could even be an inner cable that is too short for outer sleeve, inner will ride up into the instrument potentially becoming disengaged at the gearbox shaft which is crimped locally to form a square section to drive the cable. Inner cable should have a ‚ferrule’ at speedo end that prevents inner dropping too far through outer and into the wheel gearbox so disengaging at instrument and conversely ride up into the instrument so potentially disengaging at wheel gearbox. Is this ferrule fitted and secure? If buying a new cable check that the dia of the new inner is similar to that of existing. The first new cable that I bought was of smaller diameter, hence the formed square ends were not optimal and cable wouldn’t drive the Speedo. Took a while to get that resolved.
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Thanks for the advice. I'll check those out. Only been out the once.
 
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