Speedometer Bounce

Got a question. . . I just installed my newly restored Smith's gauge along with a new speedo cable (properly lubed). The gear box is also fairly new. I only had a chance to test it up to about 40 mph this evening, but I'm a little surprised to see some needle bounce. I'd say about a needle width or so each way. My question is, is a slight bounce normal on these gauges? I've heard that small bouncing is usually a cable issue, but seeing as how this is a new (supposed high quality) cable, and that I lubed it prior to installation, I don't see how that could be it. I've routed it along the swing arm and then the lower frame tube, up the forward frame tube, behind the headlight and into the gauge. I secured the cable in several places using tie-wraps. Just thought I'd run this by the forum before I call the gauge shop tomorrow.

Thanks.

John

No. Needle should be dead on still with steady speed and direct response and accurate to the mph not over reading like new fangled factory digitals. Issue likely found in the amount of insertion of cable into clock. Too far in damages clock again. Might try extra o-ring space as not enough insertion don't anything but the reading. I think I've a post on this but ain't found it yet. Someone else should detail that soon though. Once perfect - the oddometer countdown begins until it ain't of course. 2-4 rear tires worth, likely time to renew the drive again.

Hey John,

I just had mine overhauled by the local speedo shop and I observe much the same bounce as you describe. It was (a little) better when the guy ran it up off his test DC motor on the workbench. The cable ends need to be square. As they round off, the cable slops around a bit in the speedo and sender drive slots. Also, the square teeth that engage the slots on the bearing clamp on the rear wheel need to be a good (tight) fit for the same reasons. You can add braze or solder to the cable end and then file it back for a better edge and that may help. That's the extent of my knowledge I'm afraid.

Here's what I found.
quote
1. If you grease your cable, don't put grease on the top 12", if you do it will find its' way up into the instrument and will damage it.

2. The length of cable protruding into the bottom of the instrument is critical. If there is any kind of obstruction which does not allow the lower end of the inner cable to properly enter the drive, then the top end will push too far into the drive mechanism of the instrument and destroy it. We have seen many instances of this. Install the cable at the lower end (remember to secure the outer cover of the speedo cable to the lower side of the swing arm or the end fitting will break off) and examine the top end before fitting it to the instrument. If you slide the knurled nut to its highest position the tip of the inner cable should be exactly level with the top edge of the nut.
end quote

I have found most issues are the cable, cable lube, age or cable routing. You can always test the clock with a drill before whining to the repair fella.

Dave
69S

After some time the bearing and bushimgs get dry internally. Eventually your needle will break. Your need to send it in for service to one of the many places that do this. Not much else to say but to bite the bullet. $170 to $220.

Also, a cable routed too tightly to the frame can cause the inner cable to wind up and jump, to oscillate.

Thanks for the replies. After I wrote this post last night, I realized that I really don't know what kind of lubrication these cables require. This is a brand new British cable, and I was a bit surprised to see that the drive was dry. I oiled it with some 30 wt. machine oil, but wonder if that's the correct lube.

I spoke to the overhaul shop today and was advised to cut a short 4" section of my old cable and run it directly out the back of the gauge to a drill motor. If it doesn't bounce, he said, the problem is the cable. Well, it didn't bounce. He also said that installed on the bike, there will almost always be some bounce, that these gauges are not dampened. This is contrary to the experience of at least one of you.

By the way Dave, I did check the cable length. Sliding the knurled nut to the top shows the cable end flush, as you describe.

So, it would seem that leaves two possibilities. . . poor/incorrect lube, or routing, or both.

What kind of lube is recommended for the cable, and how much?

What is the proper routing, and how many spots along the cable should be tie-wraped to the frame?

Is it really true that some of you are seeing a rock steady gauge needle?

Thanks,

John

When I got my bike back, fresh from restoration, the speedo was bouncing as you describe. Brand new OEM Smith's speedo still in the original box. Windy (aka "Bill" on the Forum) switched my speedo cable for one he had in his garage and...Abra Cadabra! Everything was fine! So it might be your cable length and/or routing....or the cable itself??

I wouldn't say the clocks are rock steady, going down a road on a motorcycle and bouncing around, there is bound to be some variation, but not like a constant oscillation around a specific speed. I never noticed any 'oscillation' unless there was something wrong with the cable, lube or routing. Probably the best lube you can get is the molybdenum disulphide, rather expensive but effective and not greasy. Probably next best is graphite, again not greasy. I'm sure there will be a lot of lube opinions here. I also think Venhill makes Teflon lined cables, another option.

Dave
69S

Thanks. Any other lube ideas? What about lithium grease?

John

Any grease will help, but grease is grease, even lithium. My experience is the drier lubes are better for cables, they don't migrate to the clocks and don't make a mess and collect dirt. Graphite is pretty cheap. There is also Teflon lube in spray cans, it's not bad and it's not greasy, you might have to use it a bit more than the grease.

Dave
69S

I spent quite a time stopping my speedo needle bouncing & it was ultimately the cable lube that was the problem. I'm with Dave on the dry lube idea. I used some stuff designed for lubing bicycle cables which had Teflon in it. It's very thin & dries out once it's applied. I had to wash out the old lube to get a steady needle. I did it by leaving cable outer in situ' with both ends disconnected, removing inner cable, & pouring paraffin (kerosene?) through the cable until I thought it was clean.

This the same as the stuff I used. It has lots of uses where you need a dry lube. It's a very small bottle but a little goes a long way.

http://storckbicycles.co.cc/finish-line ... ze-bottle/

Ian

Well, the saga continues. . . I thought I had settled the bounce as much as I was going to by messing with cable positioning but it just got worse, bouncing about 10 mph either side of normal. Finally, the gauge quit again.

I packaged up the whole thing, cable and all, and sent it back to the restorer. He repaired it again and said everything checked out just fine with my British cable which he had supplied with the original repair. I got it back the other day, and It still bounces. In fact at one point it stopped again. I thought the gauge broke, but spinning it up with a drill motor proved it was fine. . . Also, no bounce with the drill motor, as long as I applied gentle forward pressure on the drill motor.

So now I figured the problem was with the gearbox. I noticed that the cable didn't seem to seat into the gearbox fitting very far, but peering inside with a flashlight didn't revel anything unusual.

I decided to call Phil Radford at Fair Spares (who sold me the Taiwanese replacement gearbox last year). Phil said that his experience is that Taiwanese gearboxes generally don't play well with British cables. He recommended buying an Emgo Taiwanese cable and said that they seem to seat into the gearbox better. Go figure.

Hopefully, I'll have a replacement cable in a week or so, and that will solve the problem. I'll let ya'll know.

You need to make sure the cable is the correct length (especially the inner cable), it goes into the gearbox correctly, and into the speedo correctly too. Don't let it push up into the speedo or you'll ruin the speedo. Also you need to make sure the cable is secured correctly, it should come off the gear box and be tied to the swing arm fairly straight. Make sure you don't have the center cable part reversed too, I had that problem and it wouldn't work right. One end of the center cable has a stop ring on it. Check that the squared ends are making good contact with the gearbox and the speedo and not rounded. I had a thread on this issue, maybe last year about this time when I was having troubles. Once I got it fettled it works fine now. As I remember, one of my centers, I had in backwards.

Dave
69S

hi, i found on mine that the nut with the two holes that screws to the wheel that the gearbox tangs sit in had been chiselled on and off lots, so the gearbox tangs wernt seating corectly and the speedo was all over the gaff. might help

Here's that old thread on the cables, it may help to go through it. speedo-cable-t9856.html?hilit=speedo

Dave
69S

The set of cable in the clock matters but usually its cable itself or speedo drive. Funny thing after I got Trixie out of the stream bed her gradually bouncing more speedo became rock steady accurate and responsive, for 10 miles, then gradually got nutzo again. Wonder what that means to the rest of you on this subject.

Well, I thought I'd resurrect this almost 3 year old thread to report what finally fixed my speedo bounce. I had tried all the recommendations given here, including cleaning out the cable sheathing and applying a teflon lube. Nothing worked. The issue was really affecting my enjoyment of the bike because not only was it irritating, I was afraid my expensive restored gauge was going to self destruct. It seemed clear to me that the problem was caused by the inner cable winding up and releasing, so I tried to figure out a way to dampen it. I finally decided to just coat the cable with the heaviest axle grease I had on hand. Then I added a second coat to be sure (being careful to avoid the top few inches). Lo and behold, that fixed it! Now the needle is smooth as silk, only bouncing slightly when I hit a bump in the road, and it's stayed that way for a good number of months. Problem solved!

Alrighty thanks for revealing this greasy shop gem to try to get steady speedo needle after all else fails.

I have had problems like this. One time a bought a new cable and it caused this problem. I spoke to a speedo specialist and he said if the new cable had been coiled up tightly and wound round it self [ you remember what we used to do ] to keep it neat, then the inner cable would get a set on it [ slight kinks ] and that was the problem. More recently I fitted a new cable and the speedo would not work. I sorted out that it was going into the speedo too much and jamming it. I ground a bit off the speedo end then found I had trouble getting it to seat because the cable was now too short. [ it was too short at the drive end now even though I took the extra off the speedo end ] It turned out that I needed a thicker spacer at the top end, to stop the cable going in too far. The cable is also rather long, and sweeps through a few bends so it will never be perfect. I have always used a lighter grease in cables and when Slick 50 grease [ Teflon impregnated ] was invented, I have only ever used that since