I'm not certain if my final drive unit is functioning ok.
It's on my workbench and when I turn the unit with my hand, it make a grating sound and stops as soon as I stop turning it.how much reistance should be felt when it's turned by hand and should it continue spinning when I let go.

Cheers

Sounds about right.

It will stop as soon as you stop turning it and you will feel some resistance  but as for a grating noise that definitely isn't normal.
There are 8 bolts around the hub where the wheel bolts if you remove them, 7mm key, you can remove the cover and see what is happening or at least see what the contents are. (oil plus whatever makes it grate)

Thanks for the replies.
The grating sound was perhaps exaggerated.


Cheers

Without any oil in it, you will hear the bearings rumble a little.

If you are in any doubt, once it's back on the bike, with the rear wheel on, grasp the wheel and try to twist it from side to side and top to bottom, there shouldn't be any noticeable play.

I don't think I'm describing the sound accurately. It definitely makes a noise when I turn the unit.
I also noticed the numbers 1 91 on the end of the splines which are in immaculate condition.
The bike is a 1984 k100. Could the numbers refer to a manufacture date?
Could it be a replacement unit?im also trying to figure out the mist effective way to clean the drive train units without having to resort to painting them.
I've used wd40 but it hasn't removed all of the blemishes?
Cheers

If the casings are the bare aluminium variety, try using brass coated wire brushes in a slow drill. Use WD40 as a lubricant/cleaning agent.

As the grime lifts, spray with more WD40 and wipe clean.

Before:



During:



Before:



After:

gabriel wrote:im also trying to figure out the mist effective way to clean the drive train units without having to resort to painting them.
I've used wd40 but it hasn't removed all of the blemishes?
Cheers

Marvel Mystery Oil + Scotch Brite pad: won't remove paint, if this is what you desire.

Simple, effective. Removes rust from chrome, too.

gabriel wrote:I don't think I'm describing the sound accurately. It definitely makes a noise when I turn the unit.
I also noticed the numbers 1 91 on the end of the splines which are in immaculate condition.
The bike is a 1984 k100. Could the numbers refer to a manufacture date?
Could it be a replacement unit?im also trying to figure out the mist effective way to clean the drive train units without having to resort to painting them.
I've used wd40 but it hasn't removed all of the blemishes?
Cheers

If it is the original 84 it will have 16 splines. From 86 on they had 20 splines.

Thanks to everyone who replied. MikeP your photos are truly inspirational.....did you apply a clear coat after you cleaned the cases?
Any particular brass wire brush needed for the clean?

Cheers

Gabriel,

I just buy a set of cheap brass-coated wire brushes (less than a Fiver here and that gets you several different sizes and shapes). As soon as the brass coating starts to wear off, stop using the brush as the steel will easily mark the aluminium.

A drill with a variable speed trigger set at a low speed helps to prevent over-working the brush and the surface, plus, using WD40 as a cleaning agent/lubricant means that it doesn't get sprayed all over the place.

As for a clear coat? No. I did that once and realised that as soon as the coat is breached and corrosion creeps under, there's no alternative but to strip it all off and begin again. Far better to just apply a decent protective polish occasionally.

I tried cleaning the underside of the swing arm with a brass coated steel brush attached to a drill.
I tried to be careful nonetheless there were scratch marks slightly visible on the swing arm.
What am I doing wrong?
I was thinking of using nylon brushes coated with aluminium oxide?
Is a polishing or cutting compound enough to remove stubborn marks from the aluminium?

Cheers

Slow speed and plenty of WD40 to lubricate and lift the dirt. Then more WD40 to wipe the surface clean.