Tach stagger

[mack]

Riding today and noticed a slight variance in the tach. Not much but the needle was jumping about 100 K worth on the tach. The motor is running smooth and real strong. No sluggishness or stagger at any RPM. Smooth as silk from 900- 7500 rpm. I have a bit of a neck strain though. "Bell" helmet.
Carbs just sync'd, color tuned and plugs gapped.
Is my Tach on the way out or is the stagger in the allowable.

[DAVINCI]

Some stagger seems to be normal for these bikes. I have had some (SOME) success in reducing it after cleaning all of the connections between the tach and the alternator

[Manny_Action_Cycle]

Tach

Since I got this bike the tach is basically useless. Have been meaning to look into this but haven't got around to it. At cruise (75mph) it jumps around from 5 to 9 randomly

[bikerphil]

Since I got this bike the tach is basically useless. Have been meaning to look into this but haven't got around to it. At cruise (75mph) it jumps around from 5 to 9 randomly

Yep, mine used to do the same. I was bored one day and took the tach apart and find corrosion on the PC board inside. Cleaned the corrosion and re-heated all the solder joints and guess what, it works like a normal tach should, go figure. YMMV

[James England]

The subject of many threads, is this one. They all do it. Mine stopped doing it after I put new ignition coils on the bike.... not sure why it stopped the tachometer from jumping. Other fixes have been detailed on the forum. Tacho jumping can indicate a charging problem, since the tacho runs off the alternator/generator. Usually, it would appear not to be the cause though.

[skids]

I have had tach "lag" while accelerating with on one of my bikes after acquiring it. The problem worked itself out. No problems at all now...

[cywelchjr]

I think that the point is, that the tach jumping means that is SOMETHING not completely right. It could be anything from a minor to a major problem. It could be the bushings the needle rides on a a bit dry, in which case if you can get some silicone lube up into there it may fix it, it could be the circuit board, the ignition circuit feeding back into the charging circuit (remember the signal the tach feeds off is very small) or a charging system problem (connection, reg/rect etc). If you can find and fix the problem, it will go away. That is IF you can find it. That said, I'm lucky in that mine doesn't wobble at all, it's not a weeble, it's nice and solid, just as my speedo is pretty much right on, right on up to the stop (verified via GPS). Now this may well (probably will) change when I change my front tire, since this is what drives it, but it shows if you can get the outside diameter of your tire just right, you might get your speedometer right, if yours works right (which is why I'm not changing mine unless it breaks), cause if it ain't broke, I ain't fixing it, and frankly, going above the pin is go to jail speed pretty much anyways, and I need neither jail time nor the added insurance cost of the speeding ticket so I'll be happy with sticking to somewhat sane speeds (and be able to claim I didn't know I was going faster if I was since the needle stops at 85 in the rare event that I actually need to go that fast).

[mack]

Tach's toast

Good news/bad news. Charging system and electrical connections are fine. Getting off the bike today I hit the handle bars and noticed the tach jump. Leaned over and hit it a rap and the needle jumped again. Crap every bump was making the needle move. So it's toast. Not that I use it much. I tend to shift by feel and sound. Really I guess they're only value is to keep you under the red line on launch starts.

[cywelchjr]

Make sure that the rubber isolation mounts are good, it sounds like it might be solid mounted which might be a problem. It jumping when jolted doesn't mean it's toast, it means everything is moving easily and smoothly, so it may just be that it's being bounced around more than it likes, that may well be an easy fix if you can figure out how to cushion it some (rubber under and over mounting bolts etc).

[Manny_Action_Cycle]

Tach

Cy,

What about dampening. I would think that the needle is supsed to be dampened (sp?). By way of an actuator or bellows? If the needle dampening is no good that could be causeing the jump?

[cywelchjr]

Nothing but the dryness of the bushing it rides in. It's actuated electronically, by magnetic coils that move it into position, but they use very small currents and very small amounts of magnetic force to do this, so it's not held all that tight. It can jiggle a bit, it's not a big deal as it's not a precision device, as a matter of fact the service manual says to NOT use it to set idle speed as it's not accurate enough.