Eratic speedo question

My speedometer had been reading a little high but now it goes along as before and, all of a sudden, it goes eradically from 70 mph to 150 mph and all over the place. I have read through some older posts on the speedo but can't find some sort of a trouble shooting guide for speedo problems that separates the different symptoms as seen to one of the three basic items (drive, cable and speedo)? I did see one cable test that I will do today and from reading, I do believe the the high reading is an adjustment thing within the speedo.

That's exactly what mine did for a week or so before not working at all.

It's now at Nisonger's being rebuilt.

Not saying yours is necessarily on the way out...but it could be.

It could be the cable length thats the problem.

I have seen this happen when the inner cable has to much slack and finds its way too far inside the speedo.

I loosened the cable and pulled it down a bit, rode around and it worked fine. If i screwed it in tight it would jump. Although the cable spun fine furing inspection it was to long.

Interesting that the cable could do that.

When I first got my 750 the needle would bounce around, although not quite that badly. It turned out the drive unit was on it's way out. It stripped out its gears not long after that. Things have been fine with the replacement drive, although it recently blew grease all over the rear wheel so it may be getting ready to expire too.

I had the gauges rebuilt on my 850 because they both needed new glass, but the speedo on it flutters a bit. I'll have to swap parts around to see what the problem is. I might try loosening the cable and see if that's it. That sounds like an easy first test.

Debby

I tried loosening the cable to speedo connection but no avail. The speedo wated to jump in 10 mph increments at a slow speed. With the cable off the bike, how much on each end should the inner portion stick past the outer sheath? I agree that loosening the cable is a great first test but what is a test that lets one know whether it is the gauge or the drive if the cable checks out OK?

Try removing the cable for the speedo completely.

Tape the cable to to your handle bar so the cable is visible.

ride around the block and watch the needle. If it's not a smooth spin that rotates evenly with the road speed it could be the drive needing to be greased or replaced. If it is smooth and looks accurate then its either the speedo or maybe the cable length.

"ride around the block and watch the needle."

Should that read "ride around the block and watch the drive cable"?

I have just had a tacho returned from speedo repair uk for eratic movement and was faced with a bill for £60 for a strip down and clean, i over oiled the inner cable and some of this worked itself up into the clock.

Neil

Yellow_Cad said:

My speedometer had been reading a little high but now it goes along as before and, all of a sudden, it goes eradically from 70 mph to 150 mph and all over the place. I have read through some older posts on the speedo but can't find some sort of a trouble shooting guide for speedo problems that separates the different symptoms as seen to one of the three basic items (drive, cable and speedo)? I did see one cable test that I will do today and from reading, I do believe the the high reading is an adjustment thing within the speedo.

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In my experience, most of the speedo cables sold are too long at the speedo end. You only need about 7/16 inch sticking out past the threaded collar with the cable seated all the way down in the out housing I ran a new cable without trimming the end and it ruined my speedo. Cable pushed up too hard into the speedo and brass filings started to appear! It had the same symptoms you describe. Had to get it rebuilt. You can trim up the end of the cable with cable cutters or by wrapping tightly with electrical tape and using a hacksaw.

Erratic speedo or tach needles (less severe than what you describe) can also be caused by lack of lubrication at the drive or on the cable itself. Make sure your drive is in good shape and full of grease. I use white lithium grease on the cable. Stop the grease about 6 inches from the speedo so it doesn't work its way into the speedo and gum it up.

I went through the same process with my speedo a few months back.

there is a simple test to ensure that the cable itself is turning at the proper speed

Excerpt below from: http://www.paspeedo.com/ratio.htm
To determine the actual ratio of your vehicle, please follow the test outlined below.

1. Check if the tire pressure is the same as advised by the factory specifications.

2. Measure (by making chalk or tape marks) a distance of 52 feet 9 1/2 inches.

3. Unscrew the speedometer cable at the speedometer head.

4. Mark the inner core with a paper flag, paper clip or preferably a hairpin.

5. Push or drive the vehicle over the entire distance, counting the full and partial revolutions of the cable.

6. Always roll the vehicle towards the first (A) marking until you see the inner core start turning to eliminate the gear clearance. Before you start counting, mark the part of the vehicle that is exactly over the beginning of the line. Stop counting when the marked portion of the vehicle is exactly over the end of the line (B).

7. It is important to verify you have no gear slippage, therefore do the test three times.

8. Send the "Test Form" along with your gauge for proper calibration.

Test 1 = ________________ Full ________________ Partial
Test 2 = ________________ Full ________________ Partial
Test 3 = ________________ Full ________________ Partial

I had the # of turns the cable is supposed to make written down somewhere.....but. Anyway, the 52 feet and change is 1 / 100 th of a mile, so you should be able to do the math from the ratio written on the speedo face. At least the number of turns should be consistent from one test to another.

In my case, it was the speedo itself that needed repair, which was done quickly and cost-effectively by these guys, who had dozens of Smiths instruments line up on their benches

2246 1/2 University Ave
San Diego, CA 92104
(619) 298-5278

good luck

keith Kelly

On a pretty comprehensive link that I found in a search on this board there is a reference to what is called a flick test to determine the condition of the inner cable itself and mine seems fine. This same article says that there should only be 7/16 inch protruding at the speedo and I have a 9/16 inch protrusion. The article calls for a 5/8 inch protrusion at the drive and I have 1 3/16 inch protrusion. This speedo had been working fine up to now so is it possible that the extra length at the drive end could cause my problem? Do these inner cables increase in length with use? If no one says anything to the contrary, I will trim my cable to the article's recommendations and then try the watch the speedo end of the cable while traveling as recommended in this post. I will assume that if I see eratic movement of the trimmed, open cable at the speedo end, then my drive is the most likely culprit.

Yellow_Cad said:

On a pretty comprehensive link that I found in a search on this board there is a reference to what is called a flick test to determine the condition of the inner cable itself and mine seems fine. This same article says that there should only be 7/16 inch protruding at the speedo and I have a 9/16 inch protrusion. The article calls for a 5/8 inch protrusion at the drive and I have 1 3/16 inch protrusion. This speedo had been working fine up to now so is it possible that the extra length at the drive end could cause my problem?.

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Yes. Mine worked fine for a few hundred miles before it started bouncing around and the gold dust appeared. I have purchased several speedo cables for various bikes and all of them have been too long. When I replaced the one on my Commando, I didn't know any better and figured that if you bought a speedo cable from a Commando supply house, it would be the correct length. Wrong. Maybe this is due to different requirements for different instruments (Veglia versus Smiths) or just sloppy manufacturing of replacement parts.

Yellow_Cad said:

Do these inner cables increase in length with use?

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I wouldn't think so. At the speedo end there should be a ferrule about an inch from the end that sits in the threaded housing. It is the length from the ferrule to the speedo end that is critical. It seems the length of the inner cable protruding at the drive end is far less critical.

Yellow_Cad said:

If no one says anything to the contrary, I will trim my cable to the article's recommendations and then try the watch the speedo end of the cable while traveling as recommended in this post. I will assume that if I see eratic movement of the trimmed, open cable at the speedo end, then my drive is the most likely culprit.

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Sounds like a plan

Well, by testing the cable and it being good and by attaching the cable to the drive and observing the speedo end and it having good movement, I next partially disassembled the speedo. It appears that the eratic needle jump is in the speedo. Very light synthetic oil did not improve things but I did notice pretty substantial back and forth play in the speedo drive. From what I have read, this occurs from running with too long of a cable drive on the speedo end. Now I will try to find a good source to send it to for a rebuild. Thanks for the help on this board.

Yellow_Cad said:

Well, by testing the cable and it being good and by attaching the cable to the drive and observing the speedo end and it having good movement, I next partially disassembled the speedo. It appears that the eratic needle jump is in the speedo. Very light synthetic oil did not improve things but I did notice pretty substantial back and forth play in the speedo drive. From what I have read, this occurs from running with too long of a cable drive on the speedo end. Now I will try to find a good source to send it to for a rebuild. Thanks for the help on this board.

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There is a good place for repair not far from you. Palo Alto speedo.

I've got a similar problem with my speedo just starting to jump about. The cable had been in for years so its not a length problem and I have also just lubricated the cable and re-greased the speedo drive which hasn't fixed it Looks like I may need a speedo rebuild.

Anyone recommend a UK firm who do this? and any idea of the likely cost?

FWIW, Nisonger's rebuild costs US$165.

Well, I did send my speedo off for a rebuild but before doing, I did take it apart and there was a definite back and forth play in the internal drive unit. When I got out all of my Commando books and looked through them to see how the speedo cable was routed, I found discrepensies. It appears that the factory threaded the cable in front of the lower yoke while many individuals as well as my previous owner, threaded the cable on the rider's side of the lower yoke. I believe that the latter could put a side thrust on the speedo cable as it enters the speedo which could cause premature wear. When I hook mine back up, I'm going with the factory way even though the other route has a little cleaner look.

If you do send it to Nisonger take a good hi-res digital picture of it and send a copy along with it. I didn't do this and mine came back with a red needle. I found a clear picture of the original unit's face with the white needle and e-mailed it to them. The guy then called and said I was trying to pull a fast one because they "could tell" it was not the same unit. I said why on earth would I do that? I only have one bike and this is the way it has been for 36 years. They finally had me send it back and I got it put right but it was no fun having to argue with them.

I sent mine to Rabers but what you say about Nisonger needs to get some exposure.

batrider said:

If you do send it to Nisonger take a good hi-res digital picture of it and send a copy along with it. I didn't do this and mine came back with a red needle. I found a clear picture of the original unit's face with the white needle and e-mailed it to them. The guy then called and said I was trying to pull a fast one because they "could tell" it was not the same unit. I said why on earth would I do that? I only have one bike and this is the way it has been for 36 years. They finally had me send it back and I got it put right but it was no fun having to argue with them.

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There's a good alternative to Nisonger's on the west coast. Palo Alto Speedo. They have rebuilt two of my instruments and did a great job. Also good folks to deal with.