Speedo trouble

[Jlovvorn]

I am having trouble with my CB160 speedo, and am posting here because I think the mechanics are identical to my 305.

It's started with the speedo winding up wildly above 30, accompanied by a loud whining sound, which can be heard easily over the engine.

I thought it was the cable, so I changed it, and it happened again, so bad the needle broke!

So, I thought it was a bad speedo, and bought a replacement off eBay.

Put it on, same problem.

So, this morning I went to the trouble of replacing the drive gear on the wheel.

You know what happened next, or I would not be posting.

Two speedos, two cables, two drive units - one of these three items must have had the same problem..

Help!

[G-Man]

This is caused by something, either speedo or cable, sticking then giving way as the tension built up in the cable unsticks the problem.

It results in the wild bouncing needle that you have seen.

You can check the speedo by inserting a small flat screwdriver and spinning it between your fingers. It should be easy to get the speedo needle to move a little as you twiddle the screwdriver.

If it is stiff then you need to soften the existing grease by painting a little solvent into the input housing on the speedo then applying a tiny drop of oil. This should ease ease up the bearing and stop it sticking.

If your cable is still binding you need to check the cable and end fittings to see if anything is running dry.

Theres no guarantee that an eBay speedo is in perfect condition when you get it.

G

[conbs]

There is one lube point where the cable hooks to the speedo that you can get to as Graham has suggested. But, there are also 2 lube points inside the speedo that you cannot get to without taking the speedo apart.

It gets worse. 1 of the two inside the speedo is right under the faced plate and easy to get to. It is a little bushing and a drop of light oil is all it needs. The speedo repair guys now suggest synthetic oil, but in the past I think they used machine oil.

The worse part is the third lube point is the one you are likely having problems with. The shaft that the needle is on comes to a point and fits in a little metal cup that is down inside the magnetic cup. The magnetic cup is hooked directly to the shaft in the center of the first lube point and the speedo cable directly spins is. As the magnetic cup spins, the magnet pulls on the metal cup that fits inside of it making it want to spin the needle. There is a little watch spring that is hooked to the top shaft that the needle is on and the spring pushes back against the magnetic force. It increasingly gives a little more as the rpm's of the magnetic cup increase. The result is your needle gradually moves clockwise the faster you go as the spring gradually gives way to more increasing rpm's of the magnetic cup.

If the action of the needle is not smooth it is likely that third lube point. If you do take it apart, BE CAREFUL with that little spring or you will break/bend it and you will be sending your speedo out for a rebuild. I think one guy left the movement together and filled the magnetic cup with oil to lube that third point, but left it full. The spring couldn't overcome that much force and the needle just went all the way clockwise at low speed. I think he turned the speedo movement on its side and drained the oil out and then it worked okay. I would be worried that a bunch of dirt would get down in that third point and soon you would have problems again.

You might be able to turn the movement on its side and irrigate the magnetic cup to clean the inside before putting a small amount of lube in the cup with it right side up and wait for the oil to flow down into the bottom of the cup at the lube point.

A 50 year old speedo will have surprises inside. Everything from spider webs to rust to ??? Get it as clean as you can and get some lube in that third lube point (and the other two) and that is probably the best you can do.

One caveat: whining noise = wear. If you heard that whining noise for very long, it may be a good idea to take your movement apart to inspect that point and clean things really well.

All of this is pretty involved work and take patience, but it is not impossible. It starts with taking the bezel off. It is brass so it will split very easy (yes, I have split a couple). Take your time and go very slow. The area that splits the easiest is the bends on the corners. Just go back and forth a little at a time. Some guys use a screw driver. Some guys use paint can openers (my preference). If you get two corners to clear, you just have to loosen the other two and the bezel should slide off.

If the above seems too much, you can call Foreign Speedo Repair (San Diego) Joel Levine has done a few Dream speedo's, too. There are sure to be others. If you decide to go it your self and have a Nippon, you can get a new face decal from the decal reproduction place in Canada. The face plate for a Fuji is different and the Nippon decal won't line up. A member Jaberwoke made a pattern you can use to print your own face plate decal for a Fuji. He gave instructions with it.

Hope this helps. Best wishes on your project.

[Jlovvorn]

Thanks!

Given the disaster that ensued when I once took the back off one of my vintage Omega watches, I think I will send it out!