Oil forcing out through filler cap

[The Other PaulG]

Here's a strange one.

The bike's a late-ish 1100.

At about 5000 revs, oil starts to seep out around the front of the oil filler cap on the rocker cover. Not loads of oil, but enough to start to drip off the back of the cover after 20 minutes or so.

It's not over-filled (the bike has just started doing this and I have not had to top up the oil for ages).

It's not a dodgy cap (I had a rubbishy locking one when I noticed the seeping, so I switched back to the standard one and it continued).

As far as I can see there may be two problems.

A blocked crankcase breather? I had a bit of a look, and could not see any sign of a breather, is it directly below the airbox?

A dislodged seal within the rocker cover? The cap actually locates into a black plastic insert in the cover, and there's a bit of movement between the insert and the cover (pic below). I can easily believe that the movement would be enough to allow a seep. Should the insert be fixed absolutely solidly? If so, how do I go about firming it up? (If this is the problem, I'll squarely blame that Wunderlich locking cap for dislodging the seat because of the amount of fiddling it takes to get it to locate....)

The way it fits, though, it seems that twisting the cap into place might be intended to 'snug up' the plastic seat between the cover and the cap.

So, please has anyone had a similar problem? Can anyone answer the question about the filler cap seat?

Thanks!

Paul G
The other

 

[cookie]

i suspect a new O ring would sort it.

 

[sani]

I have the same problem but I dont take much notes
I think is a commune problem with 1150 is
I just keep toping up when needs

 

[shuck raider]

On my third O ring in four years

 

[Noddy made me]

Paul,
Mine was exactly as you described. Change the o ring on the cap and the one on the rocker.
11141340901 o ring 34p
11141340902 o ring 60p
2 min job
Regards Tony

 

[The Other PaulG]

I have the same problem but I dont take much notes
I think is a commune problem with 1150 is
I just keep toping up when needs

Yeah, I can live with the odd spot of oil finding its way onto my boots but I have a bigger concern.

During the recent cr@ppy weather I found that a small amount of rain water 'ponds' around the filler.

Although at speed, the oil only seeps out slowly, on the over-run I noticed that the engine sucks that oil back in very rapidly, and along with the oil goes the rainwater. And that's what concerns me.

PG

 

[The Other PaulG]

Paul,
Mine was exactly as you described. Change the o ring on the cap and the one on the rocker.
11141340901 o ring 34p
11141340902 o ring 60p
2 min job
Regards Tony

Thanks guys - seems it might be nice and simple (and cheap)! All this is way preferable to skinning my knuckles trying to find a half-blocked breather!

As usual, the forum has probably saved me hours of mucking around.

Cheers all.

PG

 

[sani]

Yeah, I can live with the odd spot of oil finding its way onto my boots but I have a bigger concern.

During the recent cr@ppy weather I found that a small amount of rain water 'ponds' around the filler.

Although at speed, the oil only seeps out slowly, on the over-run I noticed that the engine sucks that oil back in very rapidly, and along with the oil goes the rainwater. And that's what concerns me.

PG

The best thing is to change your O ring and the cap
As you know the water and oil cant mix together and at the high temperature it will evaporate in no time
Good luck and late me know how you get on with the new set

 

[The Other PaulG]

Good luck and late me know how you get on with the new set

Oil be sure to let you know....

 

[Keith Chapman]

PG, I would not worry too much about water going the other way. The small amount of oil is being forces out under pressure, there is no pressure to force the water in.

 

[Blackal]

If the O-ring is sound - It sounds like the breather is partially blocked.

As far as "not getting water in" goes - there is pressure forcing it back in................... Atmospheric pressure (or more accurately - the differential pressure between Atmospheric and the vacuum in the crankcase as both pistons are on the "upstroke"). Barring any difference in pressure caused by pistonring blowpast - the differential pressure should be the same, only in different directions (out/in)

On a multi-cylinder engine, with a balanced crankcase volume, I would also suspect a bit of pistonring blowpast, but on the boxer - it isn't justified in looking in that direction (yet).

Al

 

[The Other PaulG]

Update

OK, £1.20 later (I didn't ask Vines for discount) and we have new seals.

Interesting - the old seals visually looked absolutely fine, no nicks or signs of age. So there was nothing immediately to suggest they were in any way deficient.

However, when measured side by side the cap seal was visibly 'flatter' than the new one. The seal that fits into the rocker cover looked just the same as the new one (in terms of its depth), but once fitted, the plastic fitting was notably snugger.

Then, on re-fitting the plug, it just felt considerably tighter than previously.

So far the bike has been oil tight although it's far too soon to say that with any certainty. But, just the way everything has 'snugged up', I'm very confident that it's fixed.

Cheers for the help one and all.

PG

 

[pablo666]

OK, £1.20 later (I didn't ask Vines for discount) and we have new seals.

PG

Hi mate, I just had the same problem on a long trip across France
I've Googled 'Vines' and there are a number of possibilities
Can you give the web site? I'd like to order some new seals myself.

Thanks
Pablo

 

[Shep]

Hi mate, I just had the same problem on a long trip across France
I've Googled 'Vines' and there are a number of possibilities
Can you give the web site? I'd like to order some new seals myself.

Thanks
Pablo

As far as i'm aware Vines is just a BMW dealer, so any dealer should be able to help you.

Shep

 

[The Other PaulG]

Yep, and dealer should be able to help, they should be stock items.

However, Vines' website is here:

http://vinesbikes.peweb8.m25.co.uk/default.asp

Paul G

 

[Shurv]

Pablo, as you're in Northampton, nip into Wollaston, they'll have them I'm sure.

Marcus.

 

[toucan]

does anybody know what the o-ring dimensions are? i work across for a seal supplier (they don't do penguins) and could stroll over rather than be tempted by the bmw showroom.

 

[Welshman]

does anybody know what the o-ring dimensions are? i work across for a seal supplier (they don't do penguins) and could stroll over rather than be tempted by the bmw showroom.

Stop pretending you,ve blown a seal havn,t you

 

[toucan]

Stop pretending you,ve blown a seal havn,t you

no, its ice cream, i swear.