Speedo not working. Now, I think I've fixed it.

[Tripodtiger]

G'day,
I had the front wheel out to change tyres, put it back together and the speedo has decided to stop working.
Power to the speedo.  Trip meter and odometer digits display, it switches between the two function ok.

I pulled the front wheel out again and the only thing that appeared a bit odd was that the speedo drive ring was loose behind the seal.
The ring had a couple of mm movement, along the line of the axle / spindle.
I couldn't turn the speedo drive ring behind the seal, so it was still engaged into the wheel.

Of course, I have no idea whether the speedo head engages into the drive ring properly, except to say that I can't rotate the drive head whilst it is in the correct position against the hub / drive ring - ie with the wheel out of the forks.

I've looked at the diagram in my service manual and there doesn't seem to be anything missing between the seal and the drive ring.

I popped the seal out and there doesn't appear to be any damage to any component.  It was all nicely greased and pretty clean.

Any suggestions?

[Mustang]

Girly bike?

If so look for a fubared' magnet sender

[Chris Canning]

I've found the speedo drive a law unto itself my original drive ring which I still use is in two half's I put a brand new one in and it didn't work,i'd Refit it and try again.

[Tripodtiger]

Thanks.  Been away for a few more weeks.  The 955 has been sitting, waiting.

[Tripodtiger]

It's taken me ages to get to this.  Been so many other things take priority.  It was easy enough to use the gps as a speedo.


I have bought a replacement sensor ring, speculating that the original was broken.  It's a cheap enough part to have on hand anyway.

I can't see how the speedo drive head disassembles.
The sensor ring  has rebates for the speedo drive ring to engage.
The sensor ring is outside a bright metal spacer that is integral with the assembly. Then, there is another axle spacer that has a mushroom head on it to position the wheel correctly laterally on the axle. This axle spacer slips out of the drive head with no drama.

I'm left with the dive head attached to the wires sitting in my hand.
I have cleaned the grease and debris from around the sensor drive.
The sensor drive ring looks complete and intact.  I know that hairline fractures are possible.

I can not separate the bright metal spacer or the sensor ring from the drive head.
I can't see any circlips or retaining rings or anything that looks like it holds the assembly together.
I can't see how the wiring removes from the speedo drive

If I could remember how to load photos, I would.

I've not found any videos or other threads to help me.

Looking for guidance on disassembly of the speedo drive head.

Edit.  Just found that the attachment is visible, just not while I'm editing.

In the photo, what I have called the sensor ring, is the dark part that has square rebates on opposed sides, that fits into the drive ring in the wheel.  In the next post, I have started to call that the trigger ring.
Why?  Looking at the aftermarket one I bought, it is an aluminium component with 8 steel buttons inserted around the circumference. These buttons, I assume, pass the fixed magnet inside the speedo drive head, creating an electric pulse via the Hall Effect.  Not that I know anything about that, just that it works through the disturbance of magnetic fields.  Google it, or ask an electronics engineer for the short version.
cheers

[Tripodtiger]

 

I hope I'm not going too soon on this but, it looks like I've had a win.

And perhaps something owners may also keep in mind.


The other day, I was puzzled why the trigger ring (what I've been calling the sensor ring) in the speedo drive head would not rotate.  It just had to be wrong.  Also, it didn't appear to be damaged - hairline cracks notwithstanding.

I squirted to carburettor cleaner in there and cleaned some of the 14 years of accumulated muck out. 
Then I left it to do other stuff.

Came back to it this morning and found that the trigger ring was turning.  With some resistance but it was still turning.

More carb cleaner, more cleaning. More turning, slightly easier.

Then I squirted some lanolin lubricant in there, gave it a few minutes and it turned smoother again.

So, nothing to loose, I put it back together.  Got the front wheel turning and low and behold - the speedo works.


That's made me think that, maybe, lots of the trigger ring failures are caused by crap getting past the seal and stopping the ring from rotating.  Maybe it locks up when the bike is stopped and everything cools down.  Next time the wheel rolls, the driver for the trigger ring simply smashes it.

Here then, is a suggestion.
Everytime you pull the front wheel out, give the speedo drive head a good clean and some light lubricant.

May just save some frustration


Still can't work out how it comes to pieces.  Maybe just some more lubrication?

Fingers crossed, I wont need to find out.