Speedometer gearbox spacer

Steve, sounds like you have one of the drives that has it's own locating register. Mine is the same and does not use that spacer. When I noticed it missing several years ago I bought one and found the same as you, the drive opening is too small. It's the one the bike came with 16 years ago and is an original replacement from RGM (previous owner invoice).

Previously K Glassborow wrote:

Steve, sounds like you have one of the drives that has it's own locating register. Mine is the same and does not use that spacer. When I noticed it missing several years ago I bought one and found the same as you, the drive opening is too small. It's the one the bike came with 16 years ago and is an original replacement from RGM (previous owner invoice).

Folks: After having come back to Norton twinsafter a 40 yr absence I bought a 68 Commando from a dealer (bike brought here toAus fm US and sold right on to me) and had the same query when I rebuilt the wheel hubs. (I'm damned if I could remember the exact assembly though - so back to scrutinisingthe published diagrams)

I think some of these published diagrams are not strictly correct esp as the item 31 is the spacer that locatesthe felt bearing seal behind the double slotted round speedo drive nut. It only protrudes through the drive nut enough to support the speedo drive inside face and hold it off the face of the round drive nut and wheel hub and allowing the drive grease seal to be maintained.

Heres what my onelooks like...and hoping it helps.

Patrick.

The spacer IS necessary, unfortunately as we all know the standard of Speedo gearboxes sold in the last few years has been shockingly bad, many are sold with the centre hole not big enough for the spacer not to mention the gear assemblies being made of metal akin to plastic and the end caps falling off constantly. I have a large collection of useless gearboxes in a box as do many of my commando riding friends. These have been sourced from dealers and Andover Norton. The originals lasted forever it seemed (well until after 15 - 20 years when they failed having never been greased) Now if you get a couple of thousand miles you start thinking you have a good one. I'm more convinced that the more people "collect" bikes instead of riding them then suppliers will pass off all kinds of rubbish to the end user which "looks" like an genuine part but performs as badly as a chocolate fireguard

Rant over! File out the centre and fit a spacer or when it does fall apart maybe consider the new Electronic speedo set up, might be cheaper in the long run if you are going to actually use it.

No need to rant Gino! What does the spacer actually do? I've never figured it out and have managed 35000 miles without trouble. The drive centres nicely as the hole is just large enough for the spindle. It would take a serious amount of filing to get the spacer in there. If I hadn't just painted it and refitted I'd take a pic....maybe I will cos' you've got me thinking again and that always means trouble

Without the top hat spacer, you are relying on the soft alloy of the speedo drive to clamp & hold the bearing spacer. If this gets loose it can rotate with the wheel, with the obvious disasterous results!

Thank you Tim. That makes complete sense. I've not had issues in 16 years but that has made me think........

Previously K Glassborow wrote:

Thank you Tim. That makes complete sense. I've not had issues in 16 years but that has made me think........

Sorry guys but the soft alloy body will still need to be well clamped to stop the drive moving in ANYdirection from it's required centre of the spindle. I would'nt advise any needless filing or drilling and then risk losing the centre as it is soft alloy...ugh.

I would be interested to hear if the extra top hat spacer is in fact a thin centering washer with a very short "hat" e.g. no thicker than the alloy drive center material) and used to center a drive (maye an older or other make) with an existing factory produced bigger center hole?

I just re checked mine and found no rub /damage marks inside the driveor on the circular hubdrive nut and apolished pattern of the grease seal nicely near the outer edge of the alloy hub stub.

Most importantly the clearance between the driveand the 3 hole rear wheel trim is between 25 and 35 thou (I'm not too happy about this..if anything I might fit a hard flat 50 thou washer inside between drive and item 31.) The moral being I think check it for clearance and get your grease guns out from time to time.

The top hat spacer should protrude through the speedo drive & locate in spacer item 31, when tightened, the spacer nips the alloy & at the same time pushes spacer 31 onto the inner bearing spacer, thus clamping both components. A bit belt & braces, perhaps, but Norton obviously thought it was necessary. It will all work fine without the top hat, but if there is any movement, the soft alloy wears & then the whole lot becomes loose very quickly. This I know as it happened to me twice! Since I put things back to how Norton intended, itâs never happened again. If the speedo drive hole is/was a good fit on the wheel spindle, why would you need a centering washer? It centres on the drive ring rather than the spindle/top hat.

I think Norton were the only manufacturer to use the drive with a larger hole to accommodate a top hat spacer, certainly Triumphs & BSAâs Iâve worked on from the same sort of era seem to use drives with the smaller hole that fits the wheel spindle, but both have a larger contact area for the drive to tighten onto, thus spreading the load a bit. Earlier Nortons, which donât have a top hat spacer, use the earlier speedo drive which is much more robust in this area.

If you space your drive out by 50 thou, you may find the drive dogs donât engage very much & wear away quite quickly, 50 thou is 1.25mm & most only engage 2-2.5mm from the start

Previously tim_gostling wrote:

The top hat spacer should protrude through the speedo drive & locate in spacer item 31, when tightened, the spacer nips the alloy & at the same time pushes spacer 31 onto the inner bearing spacer, thus clamping both components. A bit belt & braces, perhaps, but Norton obviously thought it was necessary. It will all work fine without the top hat, but if there is any movement, the soft alloy wears & then the whole lot becomes loose very quickly. This I know as it happened to me twice! Since I put things back to how Norton intended, itâs never happened again. If the speedo drive hole is/was a good fit on the wheel spindle, why would you need a centering washer? It centres on the drive ring rather than the spindle/top hat.

I think Norton were the only manufacturer to use the drive with a larger hole to accommodate a top hat spacer, certainly Triumphs & BSAâs Iâve worked on from the same sort of era seem to use drives with the smaller hole that fits the wheel spindle, but both have a larger contact area for the drive to tighten onto, thus spreading the load a bit. Earlier Nortons, which donât have a top hat spacer, use the earlier speedo drive which is much more robust in this area.

If you space your drive out by 50 thou, you may find the drive dogs donât engage very much & wear away quite quickly, 50 thou is 1.25mm & most only engage 2-2.5mm from the start

Tim your post got me thinking about whether I shouldshift the gearbox away from the wheel a bit or not...so pulled it off again to check howmuch engagement the dogs have with the drive slots. (turns out there is plenty and I will leave as is).

What I did discover was that my box has the larger centre hole (looks original 'as built') which matches the dia of the item 31 hole (you can feel it with the finger). I'd forgotten that the bearing side of item 31 fits over the projecting thin walledstub of the wheel bearing spacer. (in fact as you rightly said) The bore of the item 31 is parallel; so results in a nicely centralised item 31 and a gap all round the spindle at the g/box end. The box iscurrently being held central to the spindle axisby the close fit of the engaged dogs and circular drive. I've att a pic of the drive with the spindle insertedshowing the gap. The top hat spacer should fit straight in there and will slip also on into the identical annular clearance in item 31 - no crimping just straight, safe, controlled clamping pressure on the box from both sides. I'll now need to find the correct top hat spacer...anyadvice or ID of the correct top hat spacer/source will be most welcome.( I also have taken a pic of item 31 with the spindle inserted showing the clearance if interesed?)

Sorry I have hijacked this thread a bit folks but was never happy about the speedo box and the norton parts lists/diags.

If the central hole in the box is definitely neat on the spindle I would suggest leave as is and put a 50 thou or so flat tight fitting washer on the outside to substitute for the missing rim of the tophat spacer and to give a smoother face to press on the drive when it is all clamped up.

Patrick.

Patrick, The top hat spacer you need can be found at Andover Norton,

Look for Speedo drive spacer NM13270-part number 067629, price £3.01

(Enter the part number in the search box)

Regards, Tim

Previously tim_gostling wrote:

Patrick, The top hat spacer you need can be found at Andover Norton,

Look for Speedo drive spacer NM13270-part number 067629, price £3.01

(Enter the part number in the search box)

Regards, Tim

Muchos Gracias Tim you have been a great help on this and hoping Steve is now able to resolve his original query.

Item order underway.

Patrick

Previously patrick_lindsay wrote:

Previously tim_gostling wrote:

Patrick, The top hat spacer you need can be found at Andover Norton,

Look for Speedo drive spacer NM13270-part number 067629, price £3.01

(Enter the part number in the search box)

Regards, Tim

Muchos Gracias Tim you have been a great help on this and hoping Steve is now able to resolve his original query.

Item order underway.

Patrick

Just to help finalise this. I have the top hat spacerinstalled now (via RGM same part no).

Fits neatly into the speedo gearbox and on inside item 31 centralising the whole lot nicely.

Photo att showing the spacer fitted prior to putting back the spindle etc. You can also see the necessary space between end of the top hat spacer and thin wall stub of the wheel bearing spacer.

Cheers Patrick.