Smoking heads

Zider drinker

Zider drinker

Joined
May 5, 2024
Messages
38
Age
59
Location
Somerset UK
My 1990 ST1100 has decided to start smoking a blue/grey oil smelling fine mist from the top of the engine when warm and stood in traffic.Ive noticed very fine droplets of oil on the fairing below the top of the engine.The smoke goes once underway and sometimes doesn,t reappear for the rest of the journey.Temp gauge is doing everything its meant to do although with winter here in the UK its rarely moving much.
Does this mean the head gasket is going or possibly an overfill of oil? Its only smoking on the left of the engine as your sat on the bike,never the right.
 
When did you last have the valve cover off ? Commonly the rubber heat shield mat can get caught under the cover when reassembling on the inside of the cylinder block. This will result in a small oil leak.

The valve cover rubber gasket should have sealant applied at the half moons - otherwise that leaks where the half circle forms a right angle with the flat mating surface. That is a leak that may take time to develop - but typically you will have a fine mist oil spray over the front of the crankcase.
 
Not so long ago I had a case where they'd managed to block the case-vent tube; resulting pressure blew the inboard section on a valve cover gasket out...
 
jfheath said:
When did you last have the valve cover off ? Commonly the rubber heat shield mat can get caught under the cover when reassembling on the inside of the cylinder block. This will result in a small oil leak.

The valve cover rubber gasket should have sealant applied at the half moons - otherwise that leaks where the half circle forms a right angle with the flat mating surface. That is a leak that may take time to develop - but typically you will have a fine mist oil spray over the front of the crankcase.
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I'll check under the cover as above
 
Sure sounds like a camcover gasket issue. I had an oily-smelling ST1300 when a gasket that seals a spark plug tunnel was not installed correctly, resulting in a little oil entering the plug recess and exiting through the water drain and running along the joint for the head gasket. Thought I had a blown gasket for a bit until I sussed the cause.
 
Zider drinker said:
Yes and now I'm thinking I overfilled it I'll double check oil window again once she's totally cold and level
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The ST1100 is easy to overfill. It seems to have a place where oil 'hides' if the bike has been on the side stand. Putting it on its centre stand doesn't return it to the sump, so the sight glass looks low. Fill it up to the top mark and go and ride, and the sight glass will show the level almost off the top of the glass. That caught me out a few times in the early days.

After that, if I wanted to check the oil, I made sure that I had ridden it into the garage and put it on its centre stand without leaning it over, and then letting it cool. I suppose that just running the engine for a while with the bike on the centre stand and then letting the oil settle again would do the same but I never tried that.

Never check it if the bike has been on the sidestand - not even for a moment.
 
In a long stretch I have seen and experienced the changing of the type (brand) of oil used causing the complaints you describe.
I did ask a oil engineer panel at the U of W automotive conference what caused it. It is rare, but he said clearly, we don't know, but sometimes it happens.
I have personally run into it twice, once on a customers car and once with a mechanic I worked with. Go back to the oil you used before, not the used oil but, the brand.
If changing brand is the case.
 
The reason I suggest the misting disappears is it's leaking onto the exhaust on the left hand side, it burns off and appears to go away, until next time.
But......let's no get ahead of ourselves, if you suspect an overfill then like John suggests leave it standing before checking the level. From my own experience you don't have to ride it, just put it on the centre stand and run the engine. Switch er off and leave it overnight. The level will creep up over a few hours.
I occasionally pay for an oil change and the mechanic always filled the ST a little low for that reason. Once left overnight it sat on the top line perfectly.
Head gasket leaks are very uncommon, if it is leaking there is a good chance its the rocker cover gasket.
 
Upt' North said:
The reason I suggest the misting disappears is it's leaking onto the exhaust on the left hand side, it burns off and appears to go away, until next time.
But......let's no get ahead of ourselves, if you suspect an overfill then like John suggests leave it standing before checking the level. From my own experience you don't have to ride it, just put it on the centre stand and run the engine. Switch er off and leave it overnight. The level will creep up over a few hours.
I occasionally pay for an oil change and the mechanic always filled the ST a little low for that reason. Once left overnight it sat on the top line perfectly.
Head gasket leaks are very uncommon, if it is leaking there is a good chance its the rocker cover gasket.
Click to expand...
 
This makes sense,my bike lives on its side stand and I reckon I definitely didn't leave the bike long to cool down before checking level then changing oil and refilling.Ill change the oil again as it's due and this time pay abit more attention to this,failing that go to rocker cover as above.Many thanks.
 
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