Speedo Needle Position

[b.walker5]

Im in the middle of making one good speedo out of three, one not working, one trashed in an accident and one perfectly good working unit I should never have opened up. It had a dinged up bezel so i thought I would replace it with a straight one off the non working guage. I then decided that the face plate off my trashed one was in better condition so I removed, and broke, the needle to change the plate. I've changed the face plate and fitted the needle off one of the other guages but the needle now wont go back to zero, it stops at around 8kmh (5mph) and no matter where i try to push the needle on it stops in the same place. It's just a push fit on a round shaft but even when pushing it on on the wrong side of the stop and flicking the needle over it still stops at 8k. Do I have to put some preload on the hairspring and if so how much to get it to read correctly?

[3Phase]

the needle now wont go back to zero, it stops at around 8kmh (5mph) and no matter where i try to push the needle on it stops in the same place. It's just a push fit on a round shaft but even when pushing it on on the wrong side of the stop and flicking the needle over it still stops at 8k. Do I have to put some preload on the hairspring and if so how much to get it to read correctly?

Yes, there has to be a small amount of preload on the spring. You will have to 'guestimate' the amount preload (a hair or two more than 8KPH worth in your case), then ride the bike to check the accuracy; tweak it again; ride again. DO NOT bend the spring an don't flick the needle. Rotate the internal rotor (the bell-shaped part that the magnet spins) a little bit to turn the shaft, then press the needle back down.

If you bend the coil spring inside the speedometer or knock the rate adjuster out of kilter the speedometer will still work but it will be wrong and you'll need a speedometer shop to fix it.

If you mark the needle position and the internal rotor position before you remove the needle you won't have to go through the trial and error method. Just align the marks, put the needle back on and close it up.


Regards,

Scott

[b.walker5]

Okay, thanks. Now I just have to jerry rig my GPS on the bike to do a speed check. Isn't hindsight wonderful, I have now read your thread on repairing a speedo, and marking the drive and thought "bugger, why didn't i think of that". Question, your pics show a reassembled speedo, before it's fitted to the bike, without a needle Did you have to open it twice??

[3Phase]

Question, your pics show a reassembled speedo, before it's fitted to the bike, without a needle Did you have to open it twice??

I've had the speedometers and tachs opened up several times for repairs, part swaps and to take pictures. The 160MPH with the needle was and is on my bike, not on the desktop getting dismantled for science.

That particular speedometer doesn't have a needle because that was the original Federally manadated 85MPH speedometer. It donated many parts to the cause and became the 'demo' unit when I found and repaired a 160MPH speedometer.


A tip until you get the speedometer dialed in: don't crimp the faceplate ring down all the way at the corners, just lightly crimp the center on all four sides so you can R&R the speedometer without ruining the ring.


Regards,

Scott

[b.walker5]

....A tip until you get the speedometer dialed in: don't crimp the faceplate ring down all the way at the corners, just lightly crimp the center on all four sides so you can R&R the speedometer without ruining the ring.
Regards,

Scott

Not an easy thing to do since it's a round one I'm going to temp mount it in the can without the bezel and glass till I get it sorted.

[3Phase]

Not an easy thing to do since it's a round one I'm going to temp mount it in the can without the bezel and glass till I get it sorted.

Silly Kiwi -- if you leave off the faceplate the speedometer will fall out!


Regards,

Scott

[b.walker5]

Silly Kiwi -- if you leave off the faceplate the speedometer will fall out!


Regards,

Scott

Haa.. You've obviously never heard of number 8 wire and duct tape. With that we can do anything, hell we taught McGyver some of his best tricks..

[3Phase]

Haa.. You've obviously never heard of number 8 wire and duct tape. With that we can do anything, hell we taught McGyver some of his best tricks..

Well, being upside down and all at least you won't get dirt in the works!


Regards,

Scott (still in a fantastic! mood after riding my bike earlier today)