New to me 91 ST1100 blowing blue smoke

This is eerily similar to what I've got going on. I bought my '92 last night. When I went to look at it, everything seemed great. The motor was cold when I showed up to look at it, it started up just fine, no smoke. I let it run for about ten minutes to let it get up to temp, revved it some, rode it in the guy's driveway. Nothing abnormal. Trailered it home. I took it for a spin when I got home, in the dark. Everything seemed ok.

This morning when I started it up... major oil smoke out the exhaust. Maybe more on the left side than the right, but plenty from both. I rode 25 miles to work, and it was smoking the whole way. Sometimes more than others, mostly when on the throttle 'hard'. It's been sitting in the parking lot on the center stand for 2.5 hours now, and the oil level is just barely visible in the sight glass.

If I'm lucky, it was just overfilled, but I doubt it. I can't figure out why it wasn't smoking when I bought it, though...???

I guess step one is to change the oil, replace plugs, check compression, check air filter.

Bike has 178k.
 
Smoker1, yep man you need to pull those plugs to see if they are black and oily. St1100 usually don't burn oil so they tend stay full. That's not right if oil level barley visible in sight glass.
 
smoker1 said:
and the oil level is just barely visible in the sight glass.
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Do you mean it is so high you can't see the oil level at the top of the glass, or it is so low you can barely see it at the bottom??

If too high, you need to drain some off. Everyone here with an 1100 will say keep the level at the mid point between the marks. If way high, as I think you mean, oil in the pan will be contacting the crankshaft. This can create oil foaming which will get thrown up on the cylinder walls and the oil rings can only deal with so much oil before you start getting it past the rings to be burned.

You may not have noticed the smoke when you rode in the dark and the oil didn't have enough chance to foam up while doing the driveway only ride.
 
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Bush said:
The OP said blue smoke. That is oil, as coolant in the exhaust would be white.

From the initial description - "It appeared to be worse when I let off the throttle then accelerated vs. steady throttle." - this would indicate valve seals passing oil. Bad oil rings generally cause smoke all the time. If the bike sits overnight and then fires up with a cloud of blue smoke, but stops shortly after, that also indicates valve seals.

I doubt coolant is involved, but check your oil for coolant contamination by looking at the filler cap. Coolant in the oil will cause a whitish/brown mayonnaise like substance to collect there.
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???? I read it twice and didn't see "blue" either time.
 
Bush said:
Do you mean it is so high you can't see the oil level at the top of the glass, or it is so low you can barely see it at the bottom??

If too high, you need to drain some off. Everyone here with an 1100 will say keep the level at the mid point between the marks. If way high, as I think you mean, oil in the pan will be contacting the crankshaft. This can create oil foaming which will get thrown up on the cylinder walls and the oil rings can only deal with so much oil before you start getting it past the rings to be burned.

You may not have noticed the smoke when you rode in the dark and the oil didn't have enough chance to foam up while doing the driveway only ride.
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It was barely visible, on the low side.

I just started stripping it down. Oil everywhere in the air box... I wonder if it could be residual from a previous overfill?

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Jim Van said:
???? I read it twice and didn't see "blue" either time.
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Jim boy . . . what are YOU smokin' there?? That post of mine you have quoted was from THREE YEARS ago, directed at someone else on this old thread.

So a word to smoker1, the latest to have a similar problem, should be - start a new thread to get better attention to your specific problem.
 
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smoker1 said:
I just started stripping it down. Oil everywhere in the air box... I wonder if it could be residual from a previous overfill?
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Any chance the air filter is a K & N that was severely over oiled? Any idea what brand of oil is in there? A poor quality oil with little anti foaming agent (important in an engine where the oil also serves the tranny gears) could have caused oil to be sucked up the crankcase breather tube into the air box.

Clean it all up, change the oil, filled halfway between the marks and see what happens.
 
Bush said:
Any chance the air filter is a K & N that was severely over oiled? Any idea what brand of oil is in there? A poor quality oil with little anti foaming agent (important in an engine where the oil also serves the tranny gears) could have caused oil to be sucked up the crankcase breather tube into the air box.

Clean it all up, change the oil, filled halfway between the marks and see what happens.
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I started it up with the airbox lid off. After a few seconds, the hose from the crankcase started spitting a significant amount of oil into the airbox. I'm guessing this homebrewed contraption isn't helping me...
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What the heck is going on there?? There was nothing like those hoses on my '95, or my '96, but very early models DID have some other hoses coming off the rear of the engine going somewhere. I thought that was only on the '91 model though. Could be you have an early '92 model that used left over '91 engines.

That can happen, because the '96 models to Canada finally came with the PAIR system (exhaust gas recirculation), but my '96 was number 18 off the assembly line and did not have the PAIR, so I suspect I got a '95 engine in my '96 bike.
 
Bush said:
I thought that was only on the '91 model though. Could be you have an early '92 model that used left over '91 engines.

That can happen, because the '96 models to Canada finally came with the PAIR system (exhaust gas recirculation), but my '96 was number 18 off the assembly line and did not have the PAIR, so I suspect I got a '95 engine in my '96 bike.
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That's what my limited research told me as well, and I assumed the same... I must have an early '92.

So now the question is, did the original box/junction/whatever was there have some sort of filter element to keep raw oil out of the intake, or is my motor just worn out, with too much blow-by?

Thanks for the help, Bush!


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dunno what that thing is either, but hopefully it is the cause of your problem. The other possibility is you have a broken ring or something that's allowing too much piston blowby, which pressurizes the crankcase, which vents the pressurized air along with oil vapor up into the airbox through the crankcase breather tube.
 
Paging John O. who has a '91 model and may have some guidance on this. I'll send him an email, in case he isn't looking at this old thread.
 
I admit I haven't read thru all 8 pages yet, but I've seen some posts about pulling heads and what not. 40 years of wrenching has taught me this about blue smoke....

Clogged/kinked crank case breather or worn/broken rings or valve guides and seats.

Doubt it's a head gasket as that would blow white smoke and your oil sight glass would be full. And you'd smell gas or coolant in the oil fill hole.

Good luck and let's hope it's something simple.
 
Chiming in with my 91...

That pipe joint isn't factory. See my photo below. It's not hard to believe that the joint is causing oil to be sucked up. The box is to prevent oil from getting sucked up I think.



Two lines going to back of engine, one to air box. Still doesn't explain why it's puking.
 
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This is a diagram of the crankcase ventilation system on your particular bike, presumably. On my motorcycle too, I can easily plug the vent with my thumb for a brief moment without any pressure escaping. Just to give you an idea of how little pressure is supposed to be had.
 
Christianncg said:


This is a diagram of the crankcase ventilation system on your particular bike, presumably. On my motorcycle too, I can easily plug the vent with my thumb for a brief moment without any pressure escaping. Just to give you an idea of how little pressure is supposed to be had.
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I have those parts on my 1990, never get much oil in the airbox. What if the air intake was blocked, would/could that suck oil mist out of the crankcase?

That diagram (which is out of the service manual) doesn't make a lot of sense; I would have thought the lower line would be a return for any liquid oil that has separated out, so it can return to the crankcase.
 
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TerryS said:
I have those parts on my 1990, never get much oil in the airbox. What if the air intake was blocked, would/could that suck oil mist out of the crankcase?

That diagram (which is out of the service manual) doesn't make a lot of sense; I would have thought the lower line would be a return for any liquid oil that has separated out, so it can return to the crankcase.
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I'm thinking, judging by the actual position on my motor, that if the top hose is plugged on the crankcase, the bottom one will puke. The bottom one on my bike is on par with my oil level.
 
I would speak to the previous owner if that's possible, if it wasn't burning oil when you started it up then the engine didn't wear out overnight. If there has been a previous repair/alteration made then the previous owner may know all about it, he may have done it. If the breather has been altered then that's got to be your start point. My first thought was also blocked air filter hence the sucking up of the sump contents but you seem to have ruled that out. Good luck and let's hope for an easy fix.
Upt'North.
 
You sir are a victim of POS(Previous Owner Syndrome). The missing oil trap is definitely your problem and being plastic, probably broke on the PO and he was too cheap to fix it right the first time. Slam in a new one and call it a day. Most cars/trucks have a combo oil trap/PCV nowadays for the strict EPA emissions regulations.
 
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