ST1100 ... clouds of smoke, exhaust "sludge" ... then clears if ridden

Panier

Panier

Joined
Aug 10, 2018
Messages
18
Location
Northern Ireland
Hi guys

Now onto my second ST1100, bought it just before Christmas last year.

Late 1998 (registered 1999) "W" model ST1100 Pan European (UK spec) non-ABS, 45,000 miles, colour metallic green.

PO didn't ride it much, small distance commuting (not always a good thing I know), maybe about 1000 miles per year. Said he'd had it serviced last April ... with hindsight I think he meant April Fool's Day ... yes I know who the fool might be ;-D

Anyway, bike was delivered to me by a transport company, so my pre-ride checks showed it was very over-filled with oil ... top of the sight-glass! I drained it to the middle point and it started fine.

First ride, she was obviously down on one cylinder. Tested Ignition Leads, the lead to Cyl 2 was out of Ohms/range so I replaced that with a brand new one (Honda OEM). Now had spark at all plugs.

Then serviced the bike, the usual:

New oil (new 10w 40 semi-synth motorcycle oil to just the middle sight-glass marker)
new OEM oil filter
new NGK plugs gapped to spec
new OEM air filter
new carb to head rubbers
Cleaned carbs (without separating them) cleaned the bowls and lower parts of the carb thoroughly with carb cleaner, then inspected the upper diaphragms, all fine.

And then ...

When I started it after the service, after about 40 secs of idling (after turning choke off) the bike started blowing smoke out the exhaust. Grey puffs of mid-grey smoke, like burning oil but accompanied by the faint smell of fuel.

When I turned the bike off, I saw a liquid sludge at the end of each exhaust (oily but a mid-grey colour and a faint smell of fuel).

Checked the choke mechanism (perfect), crankcase breather hose and air filter and housing (perfect), no oil anywhere. Pulled the plugs and no oil on them but Cyl 2 plug still had a fuel smell.

I thought I could see oil (very clear oil, as I suppose it would be after passing through the oil filter) running down the exhaust at the header of No 4 (not Cyl 2 that had the plug issue). I tightened the exhaust flange bolts (they were loose) and this stopped - but there was obviously oil getting to there. I took the valve cover off and checked the spark plug holes/gasket - no oil anywhere there. Weird - oil in the cylinder bore?

Decided WTH, took it for a run.

Exhaust smoke (mid grey) came out the exhaust (heavier clouds of smoke on acceleration) then after about 10 minutes of riding at 50-60 mph, it totally cleared!

I stopped at a car park and it idled perfectly, didn't smoke at all, even when throttle was opened ... so I thought (hoped) all is maybe OK ... as they say, we all know how that goes.

Next day, started the bike ... same again, clouds of smoke and a bit of sludge, then clears if ridden.

Did all the checks again, no oil anywhere I can see.

I am thinking valve seals due to PO's over-filling with oil (high oil pressure?) or float bowls next.

Bike doesn't overheat and always starts fine and sounds good, seems to ride all day long with no other issues.

Sorry for long post ...

Grateful for any suggestions.
 
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My first thought is a sticky carb float. The PO could have overfilled it with oil or a sticky float combined with a faulty or bypassed fuel shut off, could have leaked fuel into a cylinder where it leaks past the rings and fills the crankcase. If you have the old oil kicking around, smell it for gas.
 
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Bmacleod said:
My first thought is a sticky carb float. The PO could have overfilled it with oil or a sticky float combined with a faulty or bypassed fuel shut off, could have leaked fuel into a cylinder where it leaks past the rings and fills the crankcase. If you have the old oil kicking around, smell it for gas.
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I actually removed the fuel shut off valve like a lot of ST1100 owners, can this cause fuel to leak into the crankcase?
 
Is it oil smoke or fuel smoke? If it is oil it could be bad valve stem seals that allows oil to leak into the cylinders after stopping the engine for a while. After starting the oil will burn off and smoke for a bit. You can run the bike this way without any ramifications other than smoking after startup and possible plug fouling. The rings may also be a little stuck from sitting - a good run for a while may loosen things up. Was there much oil residue in the air filter housing?
 
Panier said:
I actually removed the fuel shut off valve like a lot of ST1100 owners, can this cause fuel to leak into the crankcase?
Click to expand...

While this "mod" should be safe to do in most circumstances, If there is a stuck float, allowing raw fuel to leak into a cylinder, not having the fuel shut off can allow it to continue to fill the float, thereby allowing it to continue to fill a cylinder. The reference to "a faint smell of fuel" is the part that has me leaning this way

bdalameda said:
Is it oil smoke or fuel smoke? If it is oil it could be bad valve stem seals that allows oil to leak into the cylinders after stopping the engine for a while. After starting the oil will burn off and smoke for a bit. You can run the bike this way without any ramifications other than smoking after startup and possible plug fouling. The rings may also be a little stuck from sitting - a good run for a while may loosen things up. Was there much oil residue in the air filter housing?
Click to expand...

While you are correct that a leaky/worn valve seal can cause smoke, it will usually only last a second or 2, maybe 5. The owner says it smokes for 10 minutes or so. Even a stuck float like I theorized, generally wouldnt take 10 minutes to clear out. I would suggest to the OP to shut off the fuel at night to see if it makes a difference. There may be other avenues to explore as well. Kiltman had mentioned seafoam will cause grey smoke. I didnt know that, but again, why would it clear up after 10 minutes.

Burning coolant will cause white smoke. Could it possibly have a head gasket issue that seals itself up as the engine warms. That goes against usual thinking (usually an issue gets worse as the pressure builds), but hey, it wouldnt hurt to keep an eye on the coolant level
 
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Bmacleod said:
While this "mod" should be safe to do in most circumstances, If there is a stuck float, allowing raw fuel to leak into a cylinder, not having the fuel shut off can allow it to continue to fill the float, thereby allowing it to continue to fill a cylinder. The reference to "a faint smell of fuel" is the part that has me leaning this way


While you are correct that a leaky/worn valve seal can cause smoke, it will usually only last a second or 2, maybe 5. The owner says it smokes for 10 minutes or so. Even a stuck float like I theorized, generally wouldnt take 10 minutes to clear out. I would suggest to the OP to shut off the fuel at night to see if it makes a difference. There may be other avenues to explore as well. Kiltman had mentioned seafoam will cause grey smoke. I didnt know that, but again, why would it clear up after 10 minutes.


Burning coolant will cause white smoke. Could it possibly have a head gasket issue that seals itself up as the engine warms. That goes against usual thinking (usually an issue gets worse as the pressure builds), but hey, it wouldnt hurt to keep an eye on the coolant level
Click to expand...

The St1100 has a check valve in the fuel line to prevent fuel siphoning when the fuel pump is not running.

I have seen bad valve stem seals cause a lot of smoke that can take several minutes to clear up as the oil is transferred into the exhaust at startup.

The vacuum shutoff was originally put on the ST1100 to comply laws in various countries that require a positive fuel shutoff in case of an accident.
 
Keep an eye on the water and oil levels- and did you replace the oil in the 'pumpkin' - shaft drive? Don't know why, but my initial thoughts were that the bike had been drowned.....
 
bdalameda said:
The St1100 has a check valve in the fuel line to prevent fuel siphoning when the fuel pump is not running.

I have seen bad valve stem seals cause a lot of smoke that can take several minutes to clear up as the oil is transferred into the exhaust at startup.

The vacuum shutoff was originally put on the ST1100 to comply laws in various countries that require a positive fuel shutoff in case of an accident.
Click to expand...


Is that check valve independent of the fuel shut off (the part I removed)?
 
Bmacleod said:
While this "mod" should be safe to do in most circumstances, If there is a stuck float, allowing raw fuel to leak into a cylinder, not having the fuel shut off can allow it to continue to fill the float, thereby allowing it to continue to fill a cylinder. The reference to "a faint smell of fuel" is the part that has me leaning this way



While you are correct that a leaky/worn valve seal can cause smoke, it will usually only last a second or 2, maybe 5. The owner says it smokes for 10 minutes or so. Even a stuck float like I theorized, generally wouldnt take 10 minutes to clear out. I would suggest to the OP to shut off the fuel at night to see if it makes a difference. There may be other avenues to explore as well. Kiltman had mentioned seafoam will cause grey smoke. I didnt know that, but again, why would it clear up after 10 minutes.

Burning coolant will cause white smoke. Could it possibly have a head gasket issue that seals itself up as the engine warms. That goes against usual thinking (usually an issue gets worse as the pressure builds), but hey, it wouldnt hurt to keep an eye on the coolant level
Click to expand...


This is a distinct possibility considering local current weather, temps ranging from 4 to 7 degrees C. Even stop-go riding for an hour the bike warms up to the lower quarter of the temp gauge. No evidence of coolant loss. I have yet to flush the system and test the thermostat.
 
Panier said:
This is a distinct possibility considering local current weather, temps ranging from 4 to 7 degrees C. Even stop-go riding for an hour the bike warms up to the lower quarter of the temp gauge. No evidence of coolant loss. I have yet to flush the system and test the thermostat.
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Sounds like a bad thermostat. These bikes should be warming up to 3 bars (or the 1100's equivalent) in about 10 to 15 min tops. The stat closes off the engine from the radiator so the engine can warm up to operating temp, then opens to allow cool water from the radiator to replace hot water pumped from the engine to the rad. If your stat or the idle control are not working properly, you might be running on a rich mixture for longer than you want.
 
ah, thanks, so even with the fuel shut-off removed, the most that could potentially trickle in after shutdown (in a sticking float condition) is the volume of fuel left in the fuel filter?
 
Panier said:
ah, thanks, so even with the fuel shut-off removed, the most that could potentially trickle in after shutdown (in a sticking float condition) is the volume of fuel left in the fuel filter?
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:)There is also vapor pressure in the fuel tank. I don't think you have a sticking float. #2 cylinder is the closest vacuum port to the shut valve. That would explain fuel on that spark plug.. IMO
 
thanks John, I am a bit confused here, I know No 3 take-off provides vacuum for the shut-off valve (that's the one that should be disconnected/applied to a secondary source of vacuum during the carb synch. What seems to be discussed here is a separate cut-off/check valve inside the tank ... what if any cylinder is closest to that,
 
whenever i feel like buying an older bike,i read couple of these gremlin topics and that feeling goes right away :)
 
Any of your Carbs could be pressurized by the Lack of a vacuum cut-off. The mention of the vacuum shut-off on number 3 cylinder is when you have a faulty one installed it can leak fuel into the vacuum hose for that cylinder.
 
Slydynbye said:
Any of your Carbs could be pressurized by the Lack of a vacuum cut-off. The mention of the vacuum shut-off on number 3 cylinder is when you have a faulty one installed it can leak fuel into the vacuum hose for that cylinder.
Click to expand...


that's very helpful, thanks. I think I will reinstall the cut-off valve, there was nothing wrong with it I was just reading up on the subject and thought why not remove it, one less thing to go wrong ...but ironically it might make diagnosis easier if I put it back!
 
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