Topic: Why Is My Tach Pegged?

[KC_Northstar]

I just mounted the tach and speedo on my 750K project bike.  After mounting them I noticed the tach was pegged.  I know it was ok before mounting.  I removed the cable at the engine end and turned it several times by hand and the needle went back to zero.  I suppose I could have turned the cable backwards a little while mounting it.  I'm not ready to start my engine yet, so I cant test it with the engine running.   Would turning it backwards cause it to peg all the way over?

[brooze72]

Don't think so, gotta be an internal tach issue.  Is is electronic & needs a calibration?

[KC_Northstar]

Don't think so, gotta be an internal tach issue.  Is is electronic & needs a calibration?

No, Its the stock mechanical tach for a CB750 K1

[brooze72]

Ahh, the needle must be loose on the shaft!

[KC_Northstar]

OK, I know what happened.  I forgot about this.  Later on in the day after installing the gauges, I put on the kick start lever.
After installing it I cranked the engine over a couple times.  Those 1 or 2 revolutions of the engine pegged the tach.  After
reading up on how the mechanical gauges work I realize that turning them backwards should have no effect on them.
I hooked my electric drill up to the tach and it was erratic at first, but then seemed to start working OK.  I then hooked
up the speedo and the needle is all over the place.  These are gauges I bought a year ago that were supposedly completely gone
through and restored.  They look like new, but my guess is that they were only cosmetically restored.  I guess I will just use them
and see how it goes.  Maybe after some use they will be OK?  In any case it looks like I got ripped off by a Ebay seller

KC

[iron_worker]

Sounds like it's either what Brooze said that the needle is loose on the shaft, the gauge wasn't assembled properly and the needle is dragging on the face, or it wasn't lubed properly and it is sticking. All of those options suck because you will need to open them up to repair.

Did you store the gauges face down by chance? This can let the lubrication slowly run out of the lube cup inside. The grease provides a damping action so the needle operates smoothly.

IW

[KC_Northstar]

Did you store the gauges face down by chance? This can let the lubrication slowly run out of the lube cup inside.

IW

No, I knew about the issue with storing them face down.  They were stored face up.   Its not a loose needle and the needle is not
dragging on the face.  My guess is they need to be cleaned and lubed.  After running them a bit with the drill, the tach started working OK and the speedo worked most of the time, but still went erratic now and then.  Hopefully they will clear up after being run a little.  My suspicion though is that this is not a good sign.

[bjatwood]

I bet once you warm them up by running the bike down the rode they will work fine..KC