I took my R1100RT out for a couple of hundred miles last week when the
weather was nice. It's been used as a shopping barge for the last
few years so it's rare it's parked for more than three or four days.

When I got back I noticed some 'shine' on the rear tyre sidewall and the
bevel box (rear hub) was a little wet. It seems that the oil had dripped
from the drain plug and redistributed by the wind.

On closer inspection the drain plug was properly seated. The (small
amount) of oil that had leaked had got past the, aluminium, sealing
washer via a corroded 'track' in its surface. I hadn't disturbed this
drain plug for about six years. Odd that the corrosion would occur
when it was clamped between two pieces of metal (the drain plug
and the housing). Anyway, oil changed which was due and a new
washer fitted and I think we're ok for another few years.

I suppose BMW knew what they were doing when they recommended
these were changed at each oil change.

Apologies for the bike related content and the tedious nature.

On Sat, 2 Apr 2022 10:21:39 -0700 (PDT), Stephen Packer
<stephen.packer@gmail.com> wrote:

>I took my R1100RT out for a couple of hundred miles last week when the
>weather was nice. It's been used as a shopping barge for the last
>few years so it's rare it's parked for more than three or four days.
>
>When I got back I noticed some 'shine' on the rear tyre sidewall and the
>bevel box (rear hub) was a little wet. It seems that the oil had dripped
>from the drain plug and redistributed by the wind.
>
>On closer inspection the drain plug was properly seated. The (small
>amount) of oil that had leaked had got past the, aluminium, sealing
>washer via a corroded 'track' in its surface. I hadn't disturbed this
>drain plug for about six years. Odd that the corrosion would occur
>when it was clamped between two pieces of metal (the drain plug
>and the housing). Anyway, oil changed which was due and a new
>washer fitted and I think we're ok for another few years.
>
>I suppose BMW knew what they were doing when they recommended
>these were changed at each oil change.
>
>Apologies for the bike related content and the tedious nature.

Get thee hence, Evil Biker Scum!

--

-Pip

On 02/04/2022 18:21, Stephen Packer wrote:
> I took my R1100RT out for a couple of hundred miles last week when the
> weather was nice. It's been used as a shopping barge for the last
> few years so it's rare it's parked for more than three or four days.
>
> When I got back I noticed some 'shine' on the rear tyre sidewall and the
> bevel box (rear hub) was a little wet. It seems that the oil had dripped
> from the drain plug and redistributed by the wind.
>
> On closer inspection the drain plug was properly seated. The (small
> amount) of oil that had leaked had got past the, aluminium, sealing
> washer via a corroded 'track' in its surface. I hadn't disturbed this
> drain plug for about six years. Odd that the corrosion would occur
> when it was clamped between two pieces of metal (the drain plug
> and the housing). Anyway, oil changed which was due and a new
> washer fitted and I think we're ok for another few years.
>
> I suppose BMW knew what they were doing when they recommended
> these were changed at each oil change.
>
> Apologies for the bike related content and the tedious nature.

What is the drain plug made of?
Galvanic corrosion perhaps.

--
Moto Morini 2C/375, Moto Morini 2C/350
Gilera 175 Sport, Husqvarna 401 Svartpilen
1937 Sunbeam Model 14 250 Sports
"Do not adjust your mind, there is a fault in the reality"

Pete Fisher <peter@ps-fisher.demon.co.uk> wrote in
news:jarmpvFn4b6U1@mid.individual.net:

> On 02/04/2022 18:21, Stephen Packer wrote:
>> I took my R1100RT out for a couple of hundred miles last week when
>> the weather was nice. It's been used as a shopping barge for the
>> last few years so it's rare it's parked for more than three or four
>> days.
>>
>> When I got back I noticed some 'shine' on the rear tyre sidewall and
>> the bevel box (rear hub) was a little wet. It seems that the oil had
>> dripped from the drain plug and redistributed by the wind.
>>
>> On closer inspection the drain plug was properly seated. The (small
>> amount) of oil that had leaked had got past the, aluminium, sealing
>> washer via a corroded 'track' in its surface. I hadn't disturbed
>> this drain plug for about six years. Odd that the corrosion would
>> occur when it was clamped between two pieces of metal (the drain plug
>> and the housing). Anyway, oil changed which was due and a new
>> washer fitted and I think we're ok for another few years.
>>
>> I suppose BMW knew what they were doing when they recommended
>> these were changed at each oil change.
>>
>> Apologies for the bike related content and the tedious nature.
>
> What is the drain plug made of?
> Galvanic corrosion perhaps.
>

that was my thought - a lasagna cell from the effect of road salt

https://en.wikipedia.org/wiki/Galvanic_corrosion#Lasagna_cell

On Saturday, 2 April 2022 at 20:34:25 UTC+1, Pete Fisher wrote:

> > Apologies for the bike related content and the tedious nature.
> What is the drain plug made of?
> Galvanic corrosion perhaps.

Steel I think. I'll check with a magnet, it might be stainless.

On reflection I *think* it's an aftermarket one with a magnet
in it that I fitted (to gather up any little bits of ferrous gear that
made a bid for freedom).

And on secondary reflection the same bike had a minor front brake
failure for the same reason. Quite impressive how far the
brake fluid squirted when the brakes were applied. Also fixed with
copper washers.