Speedometer Not Working. Is it the gearbox or the drive dog?

Hi All! I was riding my 1981 XJ750R recently and noticed that my speedometer and odometer were no longer working! I knew that the speedometer cable was a frequent cause of this problem so I went ahead ordered a new motion-pro cable to replace it. While waiting for the cable to come I ran a few tests and I don't think that the cable is the cause of the problem. I am thinking it is the Dive Dog but I'm hoping that I can get your opinions. Here is what I have done:

-Left speedometer cable attached to speedometer and disconnected the other end of the cable from the speedometer gearbox on the wheel. I spun the cable with a drill and got my speedometer to register nearly 30 MPH. This tells me that is probably not the cable or actual speedometer.

-Lifted front end of bike and removed mudguard and caliper and spun the loose front wheel watching the end on the speedometer gearbox in hopes to see if it would turn and it did not.

-Pulled the front wheel off and removed the speedometer gearbox. I turned the gear by hand all all seemed to move freely and when moving the gear by hand I can see the end that the cable slides into turning. I greased everything all up and reattached wheel and performed the same test I ran above. Where the cable slides into speedometer gearbox was not turning again.

With all of this said I am thinking that the drive dog may have worn down. Is this common or is there something I am missing in the speedometer gearbox?

Thanks in advance!

 

Are you sure the front wheel was on the ground? The ear on the dog measures 1/4 from the flat surface to the tip. Speedo sounds about right for a drill spinning around 3k+ or so. Check to see if the tip of the speedo cable broke off

 

Re: Speedometer Not Working. Is it the gearbox or the drive

The cable is brand new and the tip looks fine. As mentioned before, the hole where the speedo cable goes into the speedometer gearbox is not rotating when the wheel rotates. I did not have the wheel touching the ground when I spun but rather lifted so it could spin freely. I will have to measure the ear on the drive dog, not sure how far it came out. I'm about 99% positive its the either the drive dog or the gear box.

 

The hole does not rotate

 

My speedometer stopped working today too. Upon inspection, mine was a snapped cable. It seems like you need a new speedometer gear.

I think this is it:
HCP1799 OEM speedometer gear drive GEAR UNIT, the large driven gear unit which your speedometer drive cable actually plugs into. For all XJ550 Maxim, all XJ650 (except Turbo), and all XJ750 models.
$ 88.95
http://xjbikes.com/Forums/viewtopic/t=1 ... rt=60.html
Check with Chacal though.

 

As I look more into your post, it could be the drive dog. That is probably the cheaper part, so you may want to experiment with that first. I would not even have thought to check that. Being that you don't need the speedometer to ride your bike, you have some room to experiment.

I think this would solve all of your issues for $34 shipped:

http://cgi.ebay.com/ebaymotors/1982-YAM ... ccessories

 

Alright, I ordered a new drive dog and retainer from Chacal and got it installed last night. After pulling the old drive dog out there was no question that it was the cause of the problem. The ears got bent down and it was pretty rusty, beyond me how that happened. Anyways, all is good again and I'm off to my next adventure. Thanks!

 

Bending the ears on the drive is a common problem. It usually happens when re-installing the front wheel and speedo drive, Some don't think about is and just put the speedo drive in the wheel with out checking the alignment. The drive dog and the slots in the drive must be aligned before putting the wheel in place or the drive dog will get bent. I'll put the speedo drive in the wheel and turn it back and fourth to make sure they are aligned.

 

Hi guys. I am new here and have a 81 xj 650 and have the exact problem vargy61 had but I'm having a hard time finding the drive dog. Any help would be appreciated.

 

Please start a thread for your bike.
The speedometer drive gear is on the left side of the front axle, between the fork leg and the wheel.
It's far more likely that your speedometer cable is broken, than for the speedo drive to be faulty.