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Oil in air box

Posted: Thu Sep 21, 2017 12:43 pm
by Karl1000
I have a 2003 twin spark 1100S. It has Irridium plugs and a Lennie's Induct fitted by the previous owner. It runs well when warm and returns upwards of 50mpg 2 up with panniers. It's not chipped, has Y piece and original cans. Throttle sync, valve clearances, coils and electrical connections + temp sensor in airbox recently checked and OK.
However it is terrible to start from cold (fine from hot). Is the oil in airbox (approx 200ml?) relating to the Lennie's (read on a previous post about the BMW original causing a small -ve pressure due to it's more restrictive nature, the Lennie's not so), a possible cause of the poor cold starting?
Is the oil due to the crankcase breather, or serious engine damage (can't be that bad, given the stats at the top, surely)?
Is it worth reverting to the original Induct and trying before taking it to a dealer for further investigation?

Thanks for any help

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Re: Oil in air box

Posted: Thu Sep 21, 2017 7:23 pm
by nab 301
Is it continually leaving oil in the airbox after draining ( via the exernal plug at the lowest point) or have you just discovered it . It's generally a mix of water/ oil/ petrol. I don't think the lennies would cause it.

Some explanation in the thread below , if it is a big problem it can be modded .
As for the poor cold starting , assuming it's not low compression... you seem to have covered everything , not sure whether an old fuel filter would affect this?
viewtopic.php?f=4&t=7905&hilit=timed+breather

Re: Oil in air box

Posted: Thu Sep 21, 2017 10:56 pm
by Karl1000
Thanks for the reply. Haven't drained it, as only just noticed it. Fuel filter recently changed! Could it be a crankcase breather problem, or is it best to bite the bullet and get it compression tested? The oil deposited doesn't look contaminated or emulsified, could that mean it has bypassed the piston/rings etc? The inlet tracts do have a slight oil film around them as well....?

Re: Oil in air box

Posted: Thu Sep 21, 2017 11:04 pm
by boxerscott
Drain it, (as per previous comment) monitor it, the engine breather is the most likely source, the 200ml you refer to can have accumulated over time.

BTW what air filter have you got in?

Chris

Re: Oil in air box

Posted: Thu Sep 21, 2017 11:16 pm
by boxerscott
Drain it, (as per previous comment) monitor it, the engine breather is a possible source, the 200ml you refer to can have accumulated over time. Go for a run with a mate and give it a good caning see if you are exhausting blue smoke, good indicator of engine wear.

Chris

Re: Oil in air box

Posted: Thu Sep 21, 2017 11:19 pm
by Mitch1100
Engine crank case vents into the air box so finding an oil film or a bit of oil there is normal. Don't overfill.

Re: Oil in air box

Posted: Fri Sep 22, 2017 9:28 am
by Karl1000
Air filter is standard BMW one I think. Has paper fan element....
Will get on to draining it ASAP. Is it worth swapping out the Lennie's for the standard ducting whilst accessing the filter housing?

Re: Oil in air box

Posted: Fri Sep 22, 2017 4:44 pm
by nab 301
Karl1000 wrote: Is it worth swapping out the Lennie's for the standard ducting whilst accessing the filter housing?

Yeah , I'll give you 50 quid for it if you don't want it... :wink:

Re: Oil in air box

Posted: Fri Sep 22, 2017 4:54 pm
by Karl1000
I'll let you know if you really want it, PM me. It won't be done until late next week.

Re: Oil in air box

Posted: Fri Sep 22, 2017 7:43 pm
by Al
Mine used to have oil in airbox occasionally, especially if it was very warm or some muppet had slightly overfilled it during a service :oops: so have to agree with Mitch, def not the induct pipe, as you have the lennies you might want to think about fitting a k&n or similar air filter.

Al

Re: Oil in air box

Posted: Fri Sep 29, 2017 2:29 am
by Hay Ewe^
Oil in the airbox:-

cant come from the combustion side of the pistons, there is no hose / conenction to the airbox from there.
cant come from the lennies inlet duct because there is no oil connection there.

There is a a breather hose - as somebody mentioned - from the crankcase to the air box and if the engine is slightly overfilled then it will vent to the airbox.
I dont think that the slightly reduced airbox pressure (if that occurs) would make a difference to 'sucking' up oil from the cranks case to the airbox. This would require more energy and as energy takes the easiest path, if the airbox is a lower pressure than standard, the inlet duct would breath more air in at an increased velocity.

I wouldn't change the lennies duct at this point.
Clean the airbox and monitor.
Check your oil level (should be midway on the sight glass)

If the oil does reappear to significant volume, then change the lennies duct just to see - at least that way you are eliminating a possibility.

Re: Oil in air box

Posted: Tue Oct 03, 2017 8:32 pm
by HerrFlick
Had the same problem in my "S".

Disappeared when I fitted longer GS intake tubes. ($35 from wrecker).

I have Lennies InDuct and stock everything else.

As well, I gained A LOT of bottom - mid-range torque, with more low rpm flexibility.
No loss of top end, with a broader power spread.
15-20% better economy.
No surging.
Easier starting and idling.

I use BP Ultimate 98 octane.
Will have to check my CCP jumper.

Dyno comparison results available.


Cheers
John C.