Smiths Speedometer drive Rebuild Explained...(2013)

I am going thru another speedo drive and thought it would be good to post some pictures and answer a few how to questions.

Here is an exploded picture, showing the location of the various components.

Once you see how everything is put together, it starts to make some sense of how it works and what can go wrong.

The wiper retainer is simply pressed in, easily pried loose with a large flat blade screwdriver.

The input spigot and cap are both pressed in, once one is removed the other one is easy to remove. This is the hardest part of the whole process.

Thanks! that explains how mine fell apart while I was riding awhile back...I saw the speedo falter and then die but did not stop to find the parts as I wrongly assumed maybe the cable had broken...anyway that will indeed be a big help if I need to rebuild one someday

Thanks, now . . . . finally . . . . I have a reason for why I saved those three or four old broken ones!

Any numbers on the gears relating to ratio? I have a few here in pieces with the retainers off and now can't tell which is which.

I'll bite. How did you remove the input spigot and cap? Also, the rivet? Replace rivets with small screw?

Hehe I know how he removed them, so also know the real question here is how will Brent get them to ever hold again. I think they made the end cap from left over carb pot metal over spill. The spline and shaft last as long as the rim gear stays stable which depends on the rivets in weak alloy case.

Hello,

really interesting thread. I always have the problem with my speedo drives that the input spigot gets loose over time. Maybe it's caused by screwing the cable nut. But this is the only reason why I buy new drives. Some day it is such loose, that the needle starts dancing. A possibility to fasten it would resolve nearly all my problems with speedo drives.

Ralf

Interesting. Thanks for taking the time to think of us and to post the pics.
What do you consider "rebuild parts" and from where may they be obtained?
All the Best.

Unfortunately many of the parts are unmarked. So it would be difficult to build one up correctly from a pile of parts.
If I get some time I will take some measurements. This one is a 15/12, I have a 2/1 to compare it to. I'll figure out an easy way to measure the gears.

As for removing the first cap, this was a head scratcher. The spigots are brass and the body is pot metal. I used a large side cutter at the seam, a firm squeeze started the cap moving, then I was able to use a bent needle nose pliers straddling the cap to gently pry it out. Patience pays here. Once one cap is out, a soft punch can be used to push the other one out.

As for reassembly. Both pushed in caps and spigots are knurled. If they are loose, a chisel and hammer could be used to restore the knurling.

As for the rivets, I have seen others use tiny screws from a hobby shop. I was careful when I removed mine, as they can be reused.

As for spare parts, good luck. I don't know of any sources other than cannibalization of other drives. I believe I have seen mention of someone selling the large gear.

There really are no "rebuild parts". This is mostly an exercise in cleaning and inspection. Usually the large gear wears out, rendering the drive useless.

Thanks bwolfie.

What is the collective wisdom for cleaning w/o dismantle and appropriate lubrication and frequency of lubrication?

I seem to recall some of the units came with a UK equivalent of a zerk type fitting.

Maybe this should be a new thread.

I've cleaned a few. I pull the retainer and the zerk. Wipe out as much grease as I can, then spray down with brake clean. I'll let it soak in a dish overnight. Respray, getting into all the passages and gaps. Then repack. Seems to do the trick.

I am fine with this thread being all things Smith Speedo drives.

Pulling out the retainer and zerk gives great access for a good cleaning.
And will be fine for most peoples needs.

Some cases will require a full tear down.

I am rebuilding this one for my Dunstall project and figured it was a good time to do a write up about it.

Everyone will need to do some sort of drive maintenance at some point, so why not be armed with the information.

I've also cannibalized a few, and the problem has always been the big gear getting chewed up until it had a nice little semi-circle profile on the outside. Does anyone know if it's possible to get those anywhere? If so, you could easily rebuild it whenever necessary.

I held my speedo cable with zip ties, Bad move It pulled the speedo drive apart.

Im going to try a 7/8 handlebar wire clip on the lower frame to hold the cable.
Hope its got enough room in the loop for the cable to move free PN 97-4112

Right now Im using a pipe clip PN 06-3031 on my sons Norton I raped some Good Scotch
Super 33+ black tape dont use the cheep stuff, to take up the space.

I found a smaller pipe clip in my old parts bin that worked a treat Ill try to find or buy
some more if I can.

If someone knows a place that I can get the smaller ones let me know. Please

Phil

"As for the rivets, I have seen others use tiny screws from a hobby shop. I was careful when I removed mine, as they can be reused."

You don't need the retainer or the rivets/screws. The retainer simply holds the ring gear in place for handling purposes, so it won't fall out of the housing when you take the housing out of the box or remove it from the bike. But it is not needed for operation - the axle/associated parts aligns/retains the ring gear in proper position. Actually the retainer just causes wear/small metal particles that doesn't need to happen at all as the retainer rubs agains the ring gear. Plug the 4 holes with a dab of silicone.

My speedo gear has been without the retainer since shortly after I bought the bike in '06.

My speedo was slinging grease everywhere. Is that meaning I need to rebuld or just clean and not put so much grease in it?

It also scratched the hell out of my wheel cover so I will have to replace that when I get there!

Tempted to go with a speedo that does not require the speedo drive.

warpedscout said:

My speedo was slinging grease everywhere. Is that meaning I need to rebuld or just clean and not put so much grease in it
It also scratched the hell out of my wheel cover

Click to expand...

Speedo drive gearbox?

Friction between the drive gearbox and the wheel cover can produce enough heat to melt the grease and so it gets flung out.
The lack of clearance is most likely due to the drive spacer collapsing, and is something that needs to be fixed as soon as possible.
https://www.accessnorton.com/NortonCommando/speedo-gearbox-problem.2359/

Speedo drive gearbox?

Friction between the drive gearbox and the wheel cover can produce enough heat to melt the grease and so gets flung out.
The lack of clearance is most likely due to the drive spacer collapsing, and is something that needs to be fixed as soon as possible.

Click to expand...

I have looked there before, I have been following the thread on the width of the swingarms. Mine meaasured just over 8 inches and always have a problem when I was fitting everything back together. Will be paying close attention on that when I get to putting it back together! Seems I need to push the arms out to give a little more clearance?!

Originally the brass pinion bearings are held in the diecast housing by staking the housing in alignment with a machined groove in the brass bearings. Instead of restaking the housing, which would probably crack it, I drilled and tapped the housing for 8-32 set screws.

I have four set screws and this picture shows two of them, the other pair are on the opposite side.

The gearbox housing hitting the wheel cover is a function of the gearbox being weak and pushed in towards the wheel. You will have to fix the gearbox, it could be the top hat spacer has been crushed too many times too. Your swing arm being too tight won't help either.

I also was thinking about some grub screws or similar if I pulled the brass end apart also.

Thanks wolfie.

Dave
69S