Re: more speedo woes

Posted by HH56 On 2015/2/13 23:34:14

Usually a sharp bend in the cable will exhibit a scraping noise and jerking action but if the bind is severe and cable end is worn it could be slipping at the transmission gear socket. Some cables have a crimp type fit into a receiver like piece that actually fits into the gear so that could also be causing a problem if there is a bind and the crimp loosened. You can check the cable condition by twisting the end of the exposed cable at speedo end. You should not be able to rotate it more than a few degrees to take the twist slop out of the cable. If you can rotate more than a few degrees then something is slipping.

A common problem is lack of lube so I would check for a dry bushing on the speedo input shaft. Anything that slows the spinning magnet down will affect the readout & dry lube has been a problem on many speedos to the point some have seized. You can check for this by inserting a small screwdriver or something similar in the receiver socket that can engage the square and then turning the input shaft. It should turn quite easily with no undue effort or friction. The cup and needle shaft is typically supported in two spots and has not been as much a problem. If the hair spring is able to return the needle to 0 freely then it should be OK but a tiny drop of light or clock oil wouldn't hurt.

Some units need oil directly on the edge of bushing where it enters the case but most units have a small felt filled oil hole in a protruding section of the case near threaded cable connection. The hole periodically needs a few drops of oil. On some speedos the grease on the worms and spur gear train between input shaft and odometer has dried which also causes a lot of drag.