1987/92 K75 Turning but Not Running..

[Finnmarbs]

Hey Gents,

I am new to the forum and beamers in general. I just bought a 1987 K75 with a 92' engine in it and quite a few electrical mods already on it. Bike was working fine, burning some small amount of oil but purred nonetheless. Was riding it with a buddy one day and suddenly i see a warning light come on and then it felt like the thing ran out of gas, it just stopped firing and the engine died. When I tried to restart it it would turn and i would hear a few explosions but wouldnt run. Once back home i checked the spark plugs they were wet with oil,  the warning light looks to be the oil pressure warning, and after checking the compression in the cylinders I found they were all slightly lower than recommended. (105psi,105psi,90Psi) Then I noticed the intake manifold, after the MAF sensor, came loose and there was engine oil all inside the intake air box. 

Things I have NOT checked:
Fuel Pressure and injectors
Timing
Water in my fuel tank
(Hopefully will get to these today)

Any Ideas what this could be before I start tear it apart? I am thinking it could be blown head gasket but am worried it could be a leak in one of the oil lines inside the engine.

Thanks!

[The Mighty Gryphon]

Just to get some clarification, you say the air connection between the MAF sensor and the plenum above the throttle bodies was found to be opened up.

Did this happen while you were riding?  If so, the measured airflow would go to a very low level and cause the fuel mixture to get lean.  If the air leak wasn't real bad, the engine would start to ping and possibly detonate.  As the leak got worse, the engine would stop running since it couldn't get the right mixture. 

The plenum has a negative pressure that is sent to the crankcase by a hose at the rear of the plenum near the throttle position switch.  It's hard to say what losing that negative pressure will do to the oil in the engine. 

How much oil is still in the crankcase?  You will need to do a drain and measure what comes out, including what is in the filter.  With the plugs out is it easy to turn the engine.  If so, are there any mechanical noises when the engine is turned by hand.

At this point I am inclines to think the problem was the opening of the air passage and the lean mix it caused.  Before I did anything else I would put all the air stuff back together, do an oil change to measure the oil left in the engine, put in a fresh set of plugs and see what happens.  If I could get it running it might help determine if there is any other damage.

[Finnmarbs]

Yes when I inspected the bike afterward, took the gas tank off and found the hose connection between the MAF sensor and the intake air box was wide open. Not sure if that happened while riding or was like that the whole time. And the oil level is right at the dot, funny thing is I haven't notice much of a change in the oil level.

Here is my new hypothesis (pardon my forum etiquette):
The intake hole has been there for sometime, which like you said would cause the fuel/air mix to run lean. Overtime running lean would burn the wall of the cylinder, that could cause an imperfect seal between the piston and cylinder which would explain the low compression. That would probably cause blowback, increasing the pressure in the crankcase and spitting oil into the intake..

So my plan is to inspect/clean out the plenum intake and spark plugs and put everything back together, change the oil and see what happens.

[The Mighty Gryphon]

Sounds like a good hypothesis.  About the oil mess, the plenums get nasty with oil, even on properly running engines.  If the level hasn't dropped there may not be a problem.  The only worrying thing is that you got an oil alarm meaning that you lost oil pressure.  I am hoping it occurred after the engine quit.

Put her together and keep us posted on this thread as to what happens next. 

[Laitch]

Check your oil filter to be sure it hasn't loosened or detached.

[Finnmarbs]

Well, shes back running!  I cleaned the plugs, and refitted the intake and cleaned the connectors. Only shes still burning oil, and strangely enough the oil level rose up from the dot to the max level overnight and the oil pressure warning light went off.... weird. So, I think I am going to just change the filter and change the oil. Any thoughts?

[rbm]

Max level is the dot in the centre of the sightglass.  Top of the glass is overfilled which might account for the excess oil in the airbox and oil burning.  Change the oil, and double check the filter fitment is correct when you replace it.

[Farmrjohn]

Max level is the dot in the centre of the sightglass.  Top of the glass is overfilled which might account for the excess oil in the airbox and oil burning.  Change the oil, and double check the filter fitment is correct when you replace it.

Did the max level change at some point?  The owner's manual for my '94 specifically shows the top of the ring marking on the glass as the max level, and the minimum level at thebottom of the ring marking.  The dot is right in the center.  The manual says it's approximately .6 liters/1.05 pints from the min to max level, but does caution about over filling or under filling.

[The Mighty Gryphon]

I would expect that it will take a while to burn off all the oil that is in the intake system. 

According to my owner's manual The top of  the circle is maximum oil level, and the bottom is the minimum. 

I, too, have seen the oil level mysteriously rise overnight after doing an oil change.  Don't know where it comes from. 

It's good to hear that it sounds like your engine is ok.  These brick engines are tough.

[rbm]

Did the max level change at some point?  The owner's manual for my '94 specifically shows the top of the ring marking on the glass as the max level, and the minimum level at the bottom of the ring marking.  The dot is right in the center.  The manual says it's approximately .6 liters/1.05 pints from the min to max level, but does caution about over filling or under filling.

I'll reword my posting above.  The maximum optimum oil level is to the dot.  Any more oil presents additional risks without contributing to improved engine lubrication.