Rebuilding speedo drive

gortnipper · Feb 25, 2021

My speedo drive recently puked all its grease out over the hub, so I took it off to have a look. The cable nipple locating tab was broken off, so the body is shot.

I had a spare body with a stripped ring gear, but a good cable nipple still attached. So I drilled out all the rivets and swapped all the good innards to the good body after a good clean, tapping an screwing the ring gear retainer in.

The gears now bind every 2/3 rotation or so, and if moved in reverse will work again for another partial turn. Works fine in reverse.

There was a bit of play on the shaft on the solid brass end, so I made a small bush out of some of the thinnest brass shim stock just to see if the binding stopped, which it didn't.

Any ideas?

Unfortunately, I didn't take any pics of the parts before reassembly.

gortnipper · Feb 25, 2021

Oh, and it catches even off the bike when moving it with a screwdriver.

marinatlas · Feb 25, 2021

may be it could help

marinatlas · Feb 25, 2021

Smiths Speedometer drive Rebuild Explained...(2013)

I would think that obtaining some soft metal pins and carefully cutting them to length, then tapping them in place ("mushroom" the ends) would be an easy enough fix for the four rivets on the main gear retaining ring... (that is, if your main gear is not excessively worn)

www.accessnorton.com

Smiths speedo gearbox repair

Thanks LAB, that helps. Dave 69S

www.accessnorton.com

NickZ · Feb 25, 2021

Usually when they "puke " the grease all over the hub it means that the speedo drive body is deformed enough to rub on the hub cover. The drive body heats up and the grease melts and flies out. Maybe that distortion is also causing the gears not to mesh properly.

gortnipper · Feb 25, 2021

I saw the video, I'll look at the other threads. It puked after a Ton run. I had taken it apart a few years ago and cleaned it up, and had been working well. Until it didn't.

Tornado · Feb 25, 2021

FYI: Instead of "puke" , the official technical term is "Black Star of Death".

gortnipper · Feb 25, 2021

NickZ said:
Usually when they "puke " the grease all over the hub it means that the speedo drive body is deformed enough to rub on the hub cover. The drive body heats up and the grease melts and flies out. Maybe that distortion is also causing the gears not to mesh properly.

The binding happens on the "new" old body - didnt notice it before on the old body that puked and had a broken tab. I know the old body was deformed, as I had straightened it as much as I could a few years ago. The new body looks to be straight and spins on the hub fine...backwards.

Tornado · Feb 25, 2021

My original drive (was on bike when I acquired it a few yrs ago), started B.S.oD.'ing and seemed like the body have been distorted. I flattened it back out some in a vise. Seemed to resolve but still occasionally got more seepage. Went to a new pattern drive (Emgo) and out of the box it seemed to have the binding as you describe. Comes and goes. My speedo seems to be jerky most of the time, but sometimes works well after higher speed runs.

gortnipper · Feb 25, 2021

Tornado said:
My original drive (was on bike when I acquired it a few yrs ago), started B.S.oD.'ing and seemed like the body have been distorted. I flattened it back out some in a vise. Seemed to resolve but still occasionally got more seepage. Went to a new pattern drive (Emgo) and out of the box it seemed to have the binding as you describe. Comes and goes. My speedo seems to be jerky most of the time, but sometimes works well after higher speed runs.

The binding was enough that when I spun the tire by hand after hand tightening the axle nut, I heard the cable yank on the speedo as the drive turned with the wheel.

There was some shine on some parts of the gears, and now there seems to be more play between the ring gear between the body and locating ring. Seems like too much slop is the culprit maybe.

Pattern drive here we come. I am picking one up at lunch time, and will spin it by hand before I leave to see if it runs smooth.

Tornado · Feb 25, 2021

gortnipper said:
The binding was enough that when I spun the tire by hand after hand tightening the axle nut, I heard the cable yank on the speedo as the drive turned with the wheel.

There was some shine on some parts of the gears, and now there seems to be more play between the ring gear between the body and locating ring. Seems like too much slop is the culprit maybe.

Pattern drive here we come. I am picking one up at lunch time, and will spin it by hand before I leave to see if it runs smooth.

I recall seeing a post some time back that even new drives may not have been pre-greased....so perhaps some of the problems arise from owners running new ones thinking they were greased?

gortnipper · Feb 25, 2021

I just picked up the new one. Smoother than the old one by a country mile.

Pre-greased which you can see coming out from under the felt retaining washer, and the felt is oil soaked. I will pull the zerk fitting and see if the pinion cavity is full before I install it. There is no slop between the retaining ring and the ring gear.

BTW - my speedo was jerky for the 28 of the last 30 years, until I had it professionally rebuilt by Robinson here in Auckland.

Butter.

baldy · Feb 25, 2021

Guessing the big gear slightly out of alignment. I have rebuilt the Speedo drives and it does not take much to bind.

gortnipper · Feb 25, 2021

baldy said:
Guessing the big gear slightly out of alignment. I have rebuilt the Speedo drives and it does not take much to bind.

How much is not much?

Three of the four holes line up perfectly with the other body, and the fourth screwed in but right on the body hole.

I also tried it on the hub with no retainer, same result.

RoadScholar · Feb 28, 2021

I have had a similar experience turning the ring gear with the drive in my hand; placing it back on the wheel the binding went away. It is important for the female drive collar's engagement recesses to be smooth with no buggering on the OD and drive recesses; the part (06-0317, Lockring, Rear Hub) is one of those parts that seem to engender abuse when being tightened with screw driver tips, punches and (I've seen this) chisels.

Most of the buggered lockrings can be cleaned up and returned to active duty. When the speedo drive is properly seated you should be able to measure, with a feeler gauge, about .015 to .020 clearance between the drive's seal retainer and the "hub cap", check again once the wheel is installed and properly torqued.

Best.

NORTSTER1974 · Feb 28, 2021

gortnipper said:
My speedo drive recently puked all its grease out over the hub, so I took it off to have a look. The cable nipple locating tab was broken off, so the body is shot.

I had a spare body with a stripped ring gear, but a good cable nipple still attached. So I drilled out all the rivets and swapped all the good innards to the good body after a good clean, tapping an screwing the ring gear retainer in.

The gears now bind every 2/3 rotation or so, and if moved in reverse will work again for another partial turn. Works fine in reverse.

There was a bit of play on the shaft on the solid brass end, so I made a small bush out of some of the thinnest brass shim stock just to see if the binding stopped, which it didn't.

Any ideas?

Unfortunately, I didn't take any pics of the parts before reassembly.

The best solution I came up with after playing with that junk for 40 years was to install one of these. https://www.thebonnevilleshop.com/p...ment-wheel-spacer-large-axle-3-4-pn-tbs-3701/

And one of these https://coloradonortonworks.net/cnw-tachometer-drive-blanking-plate.html plus made a couple spacers to get rid of them clock holders.
No muss, no fuss.

I'm happy

, the woman is happy

she doesn't have to wipe grease off the rear hub, and I can honestly answer the cop when he asks me "Do you know how fast you were going"?

baldy · Mar 1, 2021

If the gear works not smooth when not tight then I would just tighten it and run it on bench until it breaks in. Possible bits of debris?

Rebuilding speedo drive

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