Engineer bods, how can I repair my speedo drive?

**Ixion** · 9th February 2009, 11:48

OK. The XT speedo drive packed a sad a while ago

Pulled it apart and found the reason. Some explanation of how it works:

It's one of this removable little round gearboxes with a worm and wheel inside. The worm drives the actual cable, but we can ignore that bit. The gear wheel (which meshes with the worm , duh) is hardened steel. It has a central bore which revolves freely on the front axle. The end of the bore forms a boss , which has one side milled to form a D section. Over this boss fits a plate, about 16 gauge, which has a central bore with a flat in it . This should be a tight fit over the D of the boss. So that the D forms a drive lug, so that the plate will drive the wheel. And the plate on it's outer circumference has two lugs that engage with similar on the road wheel hub. Clear? The hub lugs engage the plate lugs, and the D hole in the middle of the plate fits over the D shaped boss on the worm wheel and drives it. OK.

The problems was that the D shape in the centre of the plate had flogged out , to form a ragged circle. Hence, no drive, plate just spins on boss.

The boss is hardened steel. Can't drill and tap even if there was room. Don't fancy trying to weld or braze it to the wormwheel, the latter would probably crack. I think (think!) the plate can probably be welded or brazed.

I tried Araldite. (there's no reason the plate ever needs to come off the boss). That worked for a while. Now it's gone again (at any rate the speedo isn't working again). I think the problem is the plate is very thin, and both the plate and the wheel are very hard and smooth - not a good key for the Araldite, and the constant back and forth load of accelerating and braking has broken the bond.

So - how can I secure it? Only thing I can think of (apart from stronger Araldite), is to try to build up the D section of the plate again with weld or bronze, and carefully file it to shape. Not the easiest task, but doable I guess. I'd prefer something else. I'm not totally comfortable about welding the plate, it "may" be hardened. Or at least heat treated.

idea?

(Yeah, I know, try the wreckers. And Yamaha don't list the innards of the drive separately, only the complete box for megadollars)

EDIT Added pictures

No 1 is the drive plate. The sticky out lugs engage with slots in the wheel hub. The round hole in the middle should not be round. There should be a straight bit on each side
No 2 is the wormwheel. You can see the flat milled on the top. That should engage with the flat on the inside of the drive plate
No3 is the plate assembled
No 4 is ditto

**Squiggles** · 9th February 2009, 12:10

what year xt?

**The Stranger:Me** · 9th February 2009, 12:19

Originally Posted by Ixion

(Yeah, I know, try the wreckers. And Yamaha don't list the innards of the drive separately, only the complete box for megadollars)

Yeah, I know you know, but what you may not know is that a whole speedo drive unit from Victoria Motorcycle Wreckers was about $25.00 landed for an old CB 400.

Sounds like a LOT of time and work for $25.00.

As you were.

**Skunk** · 9th February 2009, 12:24

I'd weld it if possible. Quick and easy. Any one up 'there' able to do it for ya? Other I will if ya post it down.

**slimjim** · 9th February 2009, 12:53

is there room to drill and fit small roll pin's..to lock together both plate to boss

**Ixion** · 9th February 2009, 13:38

Originally Posted by Skunk

I'd weld it if possible. Quick and easy. Any one up 'there' able to do it for ya? Other I will if ya post it down.

No room to drill anything, and it'd be drilling into hardened steel. I can weld it, but I'm not keen to weld onto the wheel, cos of it being hardened and tempered. Welding the plate and reforming is possible, just take a while. I suspect that originally it was a light interference fit on the boss, so a fair closeness of tolerance is needed. But, I can do it.

yeah, wreckers. I guess. I'm a bit reluctant, firstly because whenever I buy anything from a wrecker it turns out to be : worse than the part I'm trying ; not the right model; missing something vital.

It's a 2000, but I imagine they are all the same for the same (21") size front wheel.

**The Stranger:Me** · 9th February 2009, 13:54

Originally Posted by Ixion

yeah, wreckers. I guess. I'm a bit reluctant, firstly because whenever I buy anything from a wrecker it turns out to be : worse than the part I'm trying ; not the right model; missing something vital.

It's a 2000, but I imagine they are all the same for the same (21") size front wheel.

That said, when they sent me a faulty disc and I let them know, they without hesitation dispatched me another one.
Honestly they have been excellent to deal with.

**imdying** · 9th February 2009, 13:56

Considered JB Weld, bloody yanks swear by the stuff, they use it for all sorts of jobs.

**Ixion** · 9th February 2009, 14:12

Hm. That's a thought. JB Weld has a good rep, maybe better than Araldite in this sort of case.Araldite ALMOST did it, so a bit more grip might be just enough. . Bling, Sir.

**pete376403** · 9th February 2009, 14:30

EasyFlo or Silfos. They are both silver solders that are extremely strong and lower temp than welding or brazing.
You can use them with a propane bottle (no oxy). Plumbers supply outfits will sell it.

You could make another thin washer with the appropriate D shaped hole and silver solder this to the existing drive. Drop the thing in cold water while its still hot from the s/soldering and it will harden the steel as well

**imdying** · 9th February 2009, 15:00

Can an etching point bit in the mighty dremel rough the surface up to give the epoxy a little more purchase?

**Ixion** · 9th February 2009, 18:35

Added Some pcitures to the original

So far I think I like the JB Weld. It may not work, but if it doesn't it will do no damage, and a non functioning speedo is no hazard.

The other ideas could go wrong. I like to play it safe.

**Motu** · 9th February 2009, 19:17

How did you manage to ruin one of those!? I've never managed to do it,and I pack mine with beach sand for grease.It would be hard to fill that with brazing - I'd use a small MIG welder and dollop some poop along the flat section,then smooth it off on a curb stone.The MIG will get in fast without too much heat,and is pretty hard itself.

**Max Preload** · 9th February 2009, 23:26

Get a new one laser cut. You'd be suprised how cheap it is. And on such light gauge, fettling would be very minimal if needed at all.

You measure it, I'll draw it & DXF it.