Topic: Sluggish Tachometer

[DammitDan]

Hey all,

First off, my tach has stopped working correctly on the 1982 CB650.  The needle travels up and down in RPMs very very slowly, regardless of actual RPMs.  I've searched the forums and found a common cause of this is lack of lube or gummed up innards.  However, what's odd about my situation is, it was working fine yesterday.  It would flip up and down the RPM ranges like normal.  So why would it magically decide to stop working now?

Before I noticed this happening, I decided to finally dig into the tach and fix the long-burned-out bulb.  While I was in there, I noticed there was more than the single bulb wire...  there were also 2 wires going up into the bottom area of the tach.  Anyone know what these wires are for?  I can't really identify them on the wiring diagrams.  It's not an electric-assist tachometer, is it?  If that's the case, is it possible that I pinched a wire or something came unplugged and now only the tach cable is driving a normally electric-assisted drive motor, causing it to respond very slowly?

[SD750F]

DammitDan,

Sorry, no electrical assist circuit inside. I really do not know what you are seeing inside your tach but I will give you an explanation how it works and maybe you can figure it out. The tachometer cable spins a small wheel and the spinning wheel has a cup place over it with small magnets. The spinning wheel translates the rotational torque to the cup that has a hairspring to resist the spinning action, as well as return the needle pointer to a zero mark once the rotational component is removed. The cup has a couple jeweled bearings to keep all the workings fairly friction free but any thing like a lose hair can cause major problems it is wrapped around any of the mechanics. The only electrical system in the entire assembly is the two back lights...

Hope this helped.

Scott

[DammitDan]

TWO back lights?

#$%*.  I missed a light then.