Front Hub back plate coming loose

[Lambr62]

Hi,
Noticed today after going out the front hub back plate has a lot of play. It looks like the lock nut on the back plate side is working loose gradually somehow. I had to put a couple of shim washers on the end of the wheel spindle to push the back plate away from Hub to stop it rubbing. If I try to tighten up the lock nuts as much as possible the hub and back plate lock up with no movement. Think this maybe why its working loose gradually as i'm having to watch how much i tighten up to avoid the two sides locking up. Seems excessive to have to shim the back plate any further away from the hub as i said at the beginning i already have 2 shim washers on. I noticed also the wheel spindle is not as closer fit to the bearings as i would expect from experience from my previous series 3. The scooter i have now is 150 special 1966. Thanks for any help.

[Warkton Tornado No.1]

Oooops! Sounds dangerous!

Somehow, the set up you have is managing to pre-load the bearings so something is wrong. Have you missed out the tubular spacer that fits between the bearings?

[Lambr62]

Hi,
The spacer tube is definitely there. Is the purpose of this to keep the bearings a set distance apart? The front axle in my opinion is not a good fit on the bearing inner dias. I seem to recall on my previous series 3 that the axle was a good fit and could only be knocked out in one direction. To me the current set up would allow the axle to spin within the bearing without engaging the races. Thanks.

[rossclark]

The disc axle has a shoulder on it and only comes out one way.

The drum one has a nut either side.

The axle should be a firm fit in the bearings.

[Warkton Tornado No.1]

Hi,
The spacer tube is definitely there. Is the purpose of this to keep the bearings a set distance apart? The front axle in my opinion is not a good fit on the bearing inner dias. I seem to recall on my previous series 3 that the axle was a good fit and could only be knocked out in one direction. To me the current set up would allow the axle to spin within the bearing without engaging the races. Thanks.

The object of the tubular spacer is to ensure that the bearings aren’t loaded as will happen if all of the axial force is not taken by either the inner raceways or the outer raceways. In the hub’s case, all of the load should be through the inner raceways leaving the outer raceways free to rotate.

If the tubular spacer is too short or the hub bearing recesses loaded with paint or burred, then tightening the axle nuts will cause binding.

[Wack]

Provided the small spacer tube and opposite end cap stand proud of the oil seals and the inner spigot on the backplate isn't worn then the hub nuts should lock tight to prevent the backplate knocking during braking.If the two halves bind then adding 12mm gear/clutch shaft shims on top of the speedo side spacer will open them up to allow the hub to rotate with the nuts tight.For the nuts to come undone must mean the bearings are shot or not seated correctly on the speedo side and is perhaps moving in allowing the backplate to come loose? If you think about it ,when the outer link nut is tightened up this effectively locks the inner nut to the inside of the link so it can't really undo itself if all other components are fine.

[Lambr62]

Hi Wack,
. I have since found that there is a washer that has been put on the top hat spacer which I dont think should be there. In effect this means the top hat spacer is not touching the inner bearing small dia face at that side of the hub. I am going to remove the washer tonight and try again. In Stickys manual it doesn't mention any washer with top hat spacer , only on later types where you had a plain tubular space and a large washer. Whether this is where the confusion came from originally when It was rebuilt. I bought the scooter last September as a new restored and have since had to rectify a few problems since.Hopefully this us the last! Thanks.

[Wack]

Oh dear, any shims should always be fitted between the backplate and spacer tube.