rear hub mishap, advice please

[Andie]

Went for a ride today, still running in (450km so far) so taking it easy on 30mph roads, the Li started stalling in 3rd and 4th and it seemed smokier than normal, so slowed right down and headed for home. Finally stopped completely.

Pushed the bike onto the pavement and found it very hard to push, like it was in gear or brakes are on.

Top end is not seized and plug is fine.

Panels off and the rear hub is well loose - the locking screw has come out and the hub locking plate screw hole is some 10mm anti-clockwise from the hub screw hole.
Wobbles loads sideways and ticks when turned... had to semi-carry it home.



I haven't a 27mm socket but will get one tomorrow. Don't have a hub puller either, though doubt I'll need one.

Is the ticking the sound of broken bearings? Worried that the driveshaft and hub splines etc are now shot.

A lot of stress for one screw... which was nice and tight when I checked it.

Any advice greatly appreciated, as I am not an overly confident mechanic. A bit concerned that the wheel could've come off.

[MickYork]

Hard to make a call until the hub is off, but a bit puzzling that somethings preventing the hub from spinning. Suspect part of the brake unit may be damaged and fouling the hub..........but all guess work till the hub's off. Splines in the hub/layshaft may be damaged but would hope the layshaft itself is ok.

[rossclark]

I'd suspect looking at that that the splines on the hub have gone or that the centre boss beneath the locking ring has.

[Digger]

My money is on either the wrong cone or the nut wasn't tight enough when the locking ring was put on.

Looks very similar to mine after not too many miles after a "pro" restored it.

New hub sorted it but too far to carry home.

[Andie]

Thanks for the replies guys.
I'll get the hub off tomorrow and see how it goes.

[roli150lam]

Looking at your photo,the hole and thread seem to be in line?it looks like the locking screw has dug in to the locking ring tho.

[Andie]

Looking at your photo,the hole and thread seem to be in line?it looks like the locking screw has dug in to the locking ring tho.

Thanks but no, the locking ring hole is at least 10mm from the hub hole.Locking ring is well buckled too. Photos are just from my phone when it happened, so not the best.

Kudos to Innocenti for a canny design that doesn't spin the hub off though, as that could be serious.

Have calmed down a bit now, will strip and inspect and carry it forward.

thanks again.

[Andie]

took the hub off this morning- didn't need a socket or puller as nut came off by hand!

layshaft looks OK, though covered in swarf -

the Hub is chewed up.





on refitting to check the wheel spins, I'm hoping the slight horizontal up/down give is the chewed hub and not a layshaft bearing problem.

How good are new hubs? I've looked at the MB and AF ones, any recomendations? - Thank you - Andrew

[burnside]

SIL or UNI hubs seem to be absolutely fine, or try the Scootopia ones, they have very good reviews.

[Digger]

Andrew

That's exactly the same as my hub was.

Don't ditch as you can convert it into a brake show trimming tool.

[Andie]

SIL or UNI hubs seem to be absolutely fine, or try the Scootopia ones, they have very good reviews.

Thanks, I'm pleased with the scootopia stuff I've already recieved (wheels in particular) so I'll look there too.

Andrew

That's exactly the same as my hub was.
Don't ditch as you can convert it into a brake show trimming tool.

And thanks Digger. Nice S2 by the way, hope its all good now. The cone wasn't replaced and I did check the (new) grub screw myself when I fitted the engine... I guess it wore loose and braking spun the locking ring. Lesson learnt and just pleased it didn't fall off.

Gonna be off the road for a few weeks while I order the new hub, get it painted and fit it and then check the bearings Etc are OK, as I'm still not sure whether there has been any internal damage - all for a 95p screw. I'll get some locktite too.

Still, I can now remove a hub

Somewhat ironically my Li passed it's first post-rebuild MOT last thursday, and the tester gave it a good going over. These shopping trolleys are formidable beasts.

[Digger]

[Andie]

I fitted a new UNI hub with MB studs and MB cone - the book says 120 lbs/ft but I've also read 150 lbs/ft - is 120 OK? or 150? - thank you - andrew

[Wack]

I've used 120 on Ser 3's for years and never had a problem,the earlier Ser 1/2 with the diferent angled cones used the 150 ft/lb setting.

[Andie]

Thank you, yes, S3, 8 degree cone. Have adjusted accordingly!

[Warkton Tornado No.1]

I hope you do not mind a couple of ‘smartass’ observations whilst you are still, inevitably, ‘licking your wounds’ which, thankfully, are no threat to your health?

The M6 nyloc nuts on the rear hub seal plate are serving very little purpose as the nylon locking portions are not engaged with the studs.

The conical part of the hub shows signs of ‘chatter’ which confirms that the hub was loose for some time. That is not a ‘told you so’ remark but just to remind anybody that ‘best practice’ is to lap in the cone to the hub using grinding paste.

In fact, I am not advocating that other’s do this, but if the hub & cone are matched in such a manner, & there are no defects such as cracks to the splined part of the hub, then such hubs may be re-used with caution if you have faith in your own capability & a good understanding of the concept of the taper drive. The splines are there merely as a locating method until the torque via the correct method is achieved.

Unfortunately, in your instance, the splines in the hub appear to be showing signs of cracking & there appears to be a crack in the conical surface itself.

I wish you better luck with the replacement.

[Andie]

I hope you do not mind a couple of ‘smartass’ observations whilst you are still, inevitably, ‘licking your wounds’ which, thankfully, are no threat to your health?

Not at all, thank you WT1.

The M6 nyloc nuts on the rear hub seal plate are serving very little purpose as the nylon locking portions are not engaged with the studs.

After reading your reply I looked at the Spanners guide and it suggests originally 'M6 deep nuts and wavy washers' OR 'M6 Nyloc nut without washers'. removing the washers might make the difference. Can I undertake this, with my trusty torque wrench, from the hub end, one at a time?

The conical part of the hub shows signs of ‘chatter’ which confirms that the hub was loose for some time. That is not a ‘told you so’ remark but just to remind anybody that ‘best practice’ is to lap in the cone to the hub using grinding paste.

By 'chatter' i am guessing you mean dusty swarf? I will order a can of ABRO. And i am unlikely to forget to check the locking ring screw on a regular basis now

I wish you better luck with the replacement.

Thank you. I have fitted a UNI hub, which is not as pretty as the original (the locking washer is not recessed) but does seem solid enough. Also have an MB stainless locking washer kit which is much more substantial than the previous replacement, and some medium grade loctite for the locking screw.

Riding was fine this afternoon, most notably braking has improved significantly. My 53 year old hub was very worn on the brake shoe contact surface.

- I will remove the hub and apply paste as suggested.

[johnnyXS]

does anyone else think that the hub splines show insufficient bearing on the layshaft ?
It looks like the layshaft hasn't been pulled through sufficiently or the layshaft shimming is wrong somewhere?
Maybe its just me but I would have expected the splines of the hub to engage on the splines of the layshaft at least 3/4 engagement yet that hub looks like they engaged about 1/3rd ?
Could the original cone be poorly dimensioned not allowing the hub to engage fully with the layshaft?

[johnnyXS]

The splines are there merely as a locating method until the torque via the correct method is achieved.

.

are you sure of this ? I assumed that the cone is to centre the hub and prevent lateral movement of the hub along the layshaft splines and the drive was be carried by the spline engagement not friction of the hub on the cone and locknut . I'm happy to be proved wrong on this as you have considerably more experience of scoots than I.

[Warkton Tornado No.1]

The taper cone is a common tried & trusted method of drive in engineering (Morse taper for drills & mills) & automotive (front wheel bearings on FWD cars have terrific amounts of load serving the purpose of drive, braking & steering) where there will be specified amounts of pre-load.

Most motorcycles & modern scooters use a taper for driving the rotor (flywheel in our case) with the woodruff key as a ‘one toothed spline’ just for location.

Problems only arise when the key, or splines, must do the work of the cone due to an ill-fitting set-up, for whatever reason.

Fretting is due to the wear of a surface that is not seated correctly. It comes about because the surfaces are not on the same plane. Although the cone should be lapped to the hub, small variations will be tolerated when the hub is forced on to the cone & the surfaces will conform to one another adequately. The problems arise when the fit is poor or loose. They rock about & the rough surface you’ll see is due to localised stresses/rubbing that is the consequence of that. They are actually welding themselves together in minute areas then breaking apart.

You may have come across slip gauges, where you can slide one face of a gauge on to another, which is a similar process. If you recall, you should always slide ‘slips’ apart, not pull them, or damage will result.