Repair of Tachometer

DaveO

DaveO

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Was pretty pleased that the bike started easily even if the excessive revs had me leaping to turn the ignition off.

What I was less pleased about was the tacho needle leaping all over the place to the extent that I was sure it would be seriously damaged. After a lot of sucking of teeth I went to look on eBay only to find pretty poor stuff for sale, untested. The only decent one went for £130.

So I figured I'd pull it apart. What can I lose? Its broken already. At least I'll get to see the inside.

Pulled it apart and then found http://www.xs650.com/forum/showthread.php?t=31305 TwoManyXS1Bs step by step thread.

20140826_121027_WoodvilleRd.jpg


An iron magnetic disc rotates inside a metal cup. They don't touch but the faster the iron disc rotates the more it causes the cup to turn against the force of a hairspring. When the spinning stops the cup returns back to the zero position.

I couldn't see anything wrong but when I wiggled the threaded neck it wobbled and fell out. I guess it was supposed to be an interference fit. It wouldn't fit back in so I filed down the bent over edges until it fitted back in flush. I used a set of "diamond" files from a "we sell everything sort of shop" (£4)

20140826_121400_WoodvilleRd.jpg


Put a bit of grease on first where I was about to file so that filings wouldn't fly over onto the magnet and wiped off with paper tissues as I went. Used cotton buds and a dremel to clean all the grease and muck off I could get to and reassembled by putting a fillet of superglue around the cleaned edge figuring I could dremel it off again.

20140826_121148_WoodvilleRd.jpg


20140826_121039_WoodvilleRd.jpg


(It was a lot cleaner than the photos shown here.)

Re-assembled and it, so far, seems to work. Not sure if there was muck in between the cup and the disk or the disk was not being held centrally but hey, its fixed, I hope.

The guage was pretty easy to pry open provided you're patient and at least on mine (XS650B) any damage is hidden by a large rubber ring.

Hope this helps someone else.

Dave
 
Thanks Roy.

There were two little tangs to stop the shaft rotating in the plate. They didn't look like they were needed to ensure the positioning but I was careful not to file them down as they would prevent it from breaking free (again) and rotating.

Dave
 
DaveO, good pics! First time I've seen the insides of those 'angled inlet' instruments.

Looks like the entire instrument would need to be disassembled to be able to access the backside of that pot-metal drive adapter, so that you could try to re-swage the flange. There's a bit of stress in that area, what with owners trying to unscrew cables with water-pump pliers, and cables trying to bend around things.

Good write-up and pics. Let us know if the super-glue fix holds...
 
Thanks Too Many

I would imagine this was assembled in the factory using a press of some sort. It looked like if I could get it apart I was going to have to wail on it with a hammer and punch. The superglue was probably not the best choice but it was "to hand". I'll let you know how it holds up.

Dave
 
I've come around to super glue. There's a plastic toilet paper roller here that I keep fixing with it and it keeps breaking in a different place. It's kind of a hobby to see how many ways it will break and how many ways I can fix it with superglue. Sometimes gel is indicated, sometimes original liquid...
 
I need to take some time to get some pictures of a "tool" that I made to help work on a tachometer. Used it on one that will be going on my 1982 Heritage and next project is to attempt to fix the one on the 1978 Special that only goes so far u in the RPM scale.

I can a lest describe it here for now.

As you need to pry up the crimped over edge of the bezel to get the tach out of the "can" it can get a bit distorted. So what I did is take a couple layers of 1/2 thick plastic and glue them together to give me a one inch thick blank. Then chucked this blank in my metal lathe and bored a hole through one layer that was just a snug fit around the bezel.

This holds the shape of the bezel while prying the crimped edge up. To be honest I should have been a little more careful to not pry up too much at a time but the "tool" did a good job of holding the shape of the bezel

Then after doing what was needed I put the bezel and glass back in the "tooling" to hold it shape while I re-crimped the bezel.
 
OK, took a couple pictures, did not take tach out of the housing but you probably get the idea.

The small hole in the center of the "tool" was how I held the material in the lathe, Before epoxing the two layers together I had drilled a 1 1/2 inch hole in the upper half and then a hole for a bolt in the lower half that I could clamp in the collet holder for the lathe.

Bezel tool 01.JPG


Bezel tool 02.JPG
 
gggGary said:
3 1/2 years later the glue is holding?
Click to expand...

Ooh, bloody hell gggGary. I knew if I popped my head up someone would ask.

The very embarrassing answer is three and a half years on the bike is still work in progress. I'm not going to give reasons because in truth they are excuses (but suffice it to say the divorce has gone through and the house (hovel) I bought is now palatial. I've moved from one end of the country to the other, have a new job, now got a permanent home after eight changes of address in four years. I've also got a 20 foot garage and mate who is sharing it to renovate his ancient British bike. Each week we drink beers and compete to see who has made the least progress. Its like a "slow" race.


But i'm slowly running out of excuses. So watch this space. :)
 
@MaxPete thanks for the encouragement. You know what? I think I have to. Its getting beyond embarrassing. There's lots which could be done to it but only three things really that really need to be addressed to get it back on the road.

Making a start - which will include finding all the bits (and using some discipline to ensure that this doesn't become another evasion "You know, I really can't start until I've completely reorganised the garage.")
Sorting the front braking.
Sorting out the gummed up, knackered old carbs

after that cleaning, fettling and improving - and riding of course..

Do I start a thread in the garage section? Pictures? I think I can manage that.

(no chance of the Brit bike winning.)
 
I’m giving myself this morning to clean my garage - then I’m gettin’ busy on my own damned carb problem because this afternoon, I’m meeting a buddy for a BEvERage and I’m taking Lucille (my red ‘76 Standard) with me.

So, get at ‘er and git ‘er done!
 
Hi, just found this thread after searching far and wide for a solution to my speedo from an XT500. A mate has an XS650 and recommended looking here.
I’ve posted details on clock restoring on xt500.co forum.
Surprising how similar the internals are. I have dismantled three and all have various issues with the primary shaft, one as you have pointed out.
It would be great if that part was serviceable, alas not.
Instead of superglue I used liquid metal and it lasted all of 20 miles.
Just wondering if your super-glued clock has done many miles and is still working.
Many thanks.
AGR
 

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