Tachometer Woe

[Hedge36]

I've had an issue on my '83 R100S wherein the tach waggles around by +/- 500 RPM when at cruise sped (usually around 4-5K). Today it even kicked to 8K on startup - didn't like that at all.

Realizing that this is a fully electronic unit, I'm suspecting the sending unit, though I suppose something could be hinky in the tach itself.

Is this a common issue? And can anyone point me in the more likely direction?

Many thanks,
S

[daver80]

Hedge: The tach on my 86 R80 does the same thing and it was rebuilt only about 6 years ago. at 4K rpm, constant speed, it rises and falls. Never seen it jump to 8 at startup. No helpful advice, but misery loves company. Dave

[Ozie]

I have an 88 rs i had the same problem with mine there were times it would bounce 1-2k at a time. I had (what i thought at the time) an unrelated problem with my charging system. I started checking this and that till i found that the screw at the ground point was loose and very worn. Replacing the screw with a new one as well as trimming the ground wire to clean coper and replacing the terminal ring fixed both problems. Im not sure if that will help.

[R80RTJohnny]

I have an 86R80RT who since new has had a peculiar tach proplem. If the bike is parked and the speedometer is left in the sun it will not work until 2000 RPM. This will last for a few minutes then it will come back to normal.

Is there anything in particular that I should be checking for or just accept this as one of its quirks.

Thanks,

[PAULBACH]

Just purchased a used K75/3. It has 20K on the odometer. It has sat for 7 months in a heated garage, battery tender and stabil in gas.

When I first start the machine it goes click and clack and the tack jumps all over the dial. Then after a minute or so it quiets down and the behavior goes away.

Should I be concerned?

[donbmw]

Just purchased a used K75/3. It has 20K on the odometer. It has sat for 7 months in a heated garage, battery tender and stabil in gas.

When I first start the machine it goes click and clack and the tack jumps all over the dial. Then after a minute or so it quiets down and the behavior goes away.

Should I be concerned?

Your Tach cable may need some lub and the nylon gears in the tach also.

Don

[KBasa]

I've had an issue on my '83 R100S wherein the tach waggles around by +/- 500 RPM when at cruise sped (usually around 4-5K). Today it even kicked to 8K on startup - didn't like that at all.

Realizing that this is a fully electronic unit, I'm suspecting the sending unit, though I suppose something could be hinky in the tach itself.

Is this a common issue? And can anyone point me in the more likely direction?

Many thanks,
S

Interesting. My 84 does the exact same thing, but it usually only does it after I've thrashed it up to some higher rpm.

I believe some bikes have a damper in the units that dries up and needs to get replaced, but I could be remembering that wrong.

[Boxerkuh]

My tach went out all together. I send it in to get fixed and it was a broken diode. My speedometer did the same thing. I took it apart and lubricated the plastic gears and it works like a charm now. My guess is that this is a good maintenance proceedure every 50K or 10 years, or when it starts acting weird. Even our tachs and speedometer's need some service, just very infrequently. But remember that our Airheads are getting older... The youngest one would be around 11 years old now.... :stick
My food for thought.... :drink :eat

[Braddog]

Your Tach cable may need some lub and the nylon gears in the tach also.

Don

Mine on the '77 RS works OK, but squeals sometimes. What type of lube would I use? A little Mystery Oil? Silicone?

[RandyB]

There are different brands of cable oilers at most shops. Just don't lube the new control cables, as they have a nylon liner.

The speedometer can be lubed with spray silicone. The Airheads site has instructions for rebuilding and lubing.

Still looking for that ground screw that Ozie mentions. Any suggestions?