"Bouncing" tachometer needle

[preflight99]

The tachometer indicator, a.k.a. needle bounces around a lot when i am riding at hwy speeds. At idle it is fine, but when I am crusing, forget it. It also seems to work fine when reving the engine in the upper rpm range. Any ideas on to the possible cause here. The bike is a 1982 750TZ. Thanks

[herostar]

I was just about to post the same thing!

When I'm cruising above about 50 my tach will bounce around in 500-700 rpm swings while I'm cruising at constant speed. Anyone know why this is? ('81 gs450e)

[TheCafeKid]

My speedo does the same. I have tried oiling both drives (at the wheel and in the cluster) didn't seem to cure it. I think it's the actual spring mechanism in the gauges. Inthat case, if it's even repairable getting to them in most clusters requires dremel-ing the cups in half and then gluing them back together as far as I can tell.

[BassCliff]

Greetings and Salutations!!

Hi Mr. preflight99,

First, I strongly encourage you to get the RTV sealant away from your clutch cover and put a proper gasket on there. That goopy RTV will clog oil passages and break your motor.

There's no need to cut open your gauges. You can pry away the back side of the face very carefully. Mr. Nessism has a picture around here somewhere. CLICK HERE to see the thread. Inside your gauges you will find a bell housing surrounded by gear mechanisms.



The mechanism spins a magnet inside the bell housing. In turn this actuates a watch spring assembly that turns the needle. Sometimes there is gunk in the bell housing which interferes with the magnet's ability to turn the assembly as it is spinning.

Actually, I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[preflight99]

Wow, thanks for the great response! I did use black RTV, but a very thin layer and allowed it 24 hours to "skin" over before filling the oil sump. I appreciate you bringing that to my attention and will never use it again. As far as the tach or speedometer goes. Judging from the great pics you posted, it might be a issue with the spring becoming weak over time, with just enough tension to meet the needs of the tach under a light load or a high load. If so, maybe banding the outer two bands of the spring together might firm it up a little. May be way off here, what do you guys think?

[Macmatic]

New cable? My fiends GS1100 had a bouncy tach and after I cleaned it at both ends with no change I put in a new cable, et voila!

/\/\ac

[Nessism]

The bouncing needle isn't a spring issue, its more in the damping mechanism; if the spring was weak the speedo/tach would indicate higher than need be but that doesn't seem to be the case. Unfortunately, the damping mechanism is sealed and doesn't seem to be serviceable, or at least I haven't been able to figure out how to service it yet, so I'm not sure what to suggest.

[Richsuz]

My speedo does the same. I have tried oiling both drives (at the wheel and in the cluster) didn't seem to cure it. I think it's the actual spring mechanism in the gauges. Inthat case, if it's even repairable getting to them in most clusters requires dremel-ing the cups in half and then gluing them back together as far as I can tell.

A few months ago, mine started the same thing. Since the dealer has a brand new unit in stock I figure I venture and try to repair. Pryed it open, and found BLACK whatever inside the clockwork. I soaked the whole thing in WD40 for a couple of hours, cleaned and oiled completely. Not only does it work great now, I can actually see the display at night. It was so dirty inside that there was a black film behind the face. The only bad aspect of the whole thing is cosmetics, 'cause the black rim around the glass looks like someone Pryed it OPEN . But it works.

[posplayr]

A few months ago, mine started the same thing. Since the dealer has a brand new unit in stock I figure I venture and try to repair. Pryed it open, and found BLACK whatever inside the clockwork. I soaked the whole thing in WD40 for a couple of hours, cleaned and oiled completely. Not only does it work great now, I can actually see the display at night. It was so dirty inside that there was a black film behind the face. The only bad aspect of the whole thing is cosmetics, 'cause the black rim around the glass looks like someone Pryed it OPEN . But it works.

Normally you can pry the lip on the hidden side of the rim holding the glass to the front of the guage.

What "clock work" exactly did you "clean out"? Is it the "bell housing" Cliff referred to?

Ed has a pic but here are some more showing the "pry" technique. It is really pretty simple if you are a little patient. It takes about three times around the whole thing to get it bent back uniformlly enough to take the face off.

[Richsuz]

Normally you can pry the lip on the hidden side of the rim holding the glass to the front of the gauge.

What "clock work" exactly did you "clean out"? Is it the "bell housing" Cliff refered to?

And a bunch of other mecanical parts inside the housing. One looks like the old fashion clock/watch coil spring

[posplayr]

And a bunch of other mecanical parts inside the housing. One looks like the old fashion clock/watch coil spring

are you saying you simply cleaned up what you could see or you actually disassembled something other then the outside cover.

I have been inside my gauges just never tried to clean the mechanisim.

Oh and dont use brake cleaner

[WilliamGLX81]

Hey everybody...


I had a new tach cable, but a bouncing tach. This was my quick and dirty fix. It can be finessed by being more careful, and the core approach is right.

I hacksawed the gauge apart, and re-sealed it with a thin layer of ABS/pipe cement.

I've worked with PCs and felt lots of fans with bad/dry bearings. The bearings were dry - the oil had accumulated a lot of particles.

The spring works fine, and the needle would fall back correctly.
From how I saw it, the mechanism works with a sort of... magnetic slip mechanism.
In other words, the cable spins a ball, which spins the needle without making contact. The spring pulls the cable down to zero.

Anyway, the fix was to clean and re-lubricate the almost-sealed bearings.
I used WD-40 in massive doses to clean the bearings and removed a good deal of rust and old lubricant.

I replaced the grease with synthetic bicycle chain lubricant. It's probably around ...20 weight oil.
Before replacing the oil, I could spin the needle drive with my fingers, and only get the tach to move up to about 5K by hand. Afterwards, I could move the tach up to a lot higher.

I'm sure it would still be working, if the cable hadn't broken in the middle.... Heh.

I'm going to replace all my gauges, since they're all pretty thoroughly trashed. I can do a teardown and repair guide - if anyone wants - when I replace the gauges.

With the old grease, the bearings provide inconsistent resistance to spinning of the gauge drive.

-William

[chef1366]

Oh and dont use brake cleaner

But it's always handy!

[TheCafeKid]

Normally you can pry the lip on the hidden side of the rim holding the glass to the front of the guage.

What "clock work" exactly did you "clean out"? Is it the "bell housing" Cliff referred to?

Ed has a pic but here are some more showing the "pry" technique. It is really pretty simple if you are a little patient. It takes about three times around the whole thing to get it bent back uniformlly enough to take the face off.

I just did this with a set of gauges. A little added bonus to make it go a little quicker and even a little neater (making the pried edges all nice and uniform so when you press them back in they look less "messed with") was to start with one pass with the screwdriver as shown and then we switched to a pair of flat nosed pliars. They allow you to bend the pried up bezzel edge up and straight making a nice even bit, and also put no side loading forces on the bezzel itself which is how I broke the FIRST ones glass that I practiced on. (an old nasty set)

[1_v8_merc]

My Tach cover/glass already comes off, i guess the previous owner hit it or something, and had to take it apart, cause the inside tach RPM backplate is bent a little and looks like someone tried to straighten it.

How do I get the Tach needle off?
Is this going to cause springs and **** to fly everywhere?

I loosened the 2 TINY screws on the front plate, next to the needle.....but it just loosens the plate up, not the needle....

Do you just yank the needle off? lol
I don't want to break it really....although it's a piece of crap anyways.....