Still more White smoke?!

I know white smoke coming from my exhaust is burning oil. I just got a tune up and they topped it up. Should i be concerned about the smoke? its been a while since the tune up and i feel like all the excess oil should be burned out. its bad when i let it sit for a couple of days and turn it on.

Also the gas remaining in the filters slowly trickle pass the carbs and into the heads. My petcocks work fine but i'm worried if i forget them in the on position, the whole tank will want to pour in.

thoughts? advice?
I ride a 1975 r75/6

Thanks
Corey

Corey -

How long since the tune up...how many miles? Have you checked the oil level since they topped it up...assuming they put oil into the top fill mark on the dipstick. Which cylinder seems to be smoking?

A couple of thoughts relative to this:

- cheaper brands of oil sometimes tend to have the additive package burn off more quickly than others
- it's been said that Airheads engines don't like having the oil up to the top mark and that due to the air-pumping action of the pistons, the excess oil will be whipped up and more easily burned. The oil mist escapes via the engine breather and is dumped out the right carb for the /6.
- parking the bike always on the side stand does allow for oil to run down the inside of the left cylinder barrel which can then work back into the combustion chamber...smoke would primarily be the left side

As for the gas issue, if gas continues to trickle past the filters, then it would seem that the petcock is not working. If the petcock is off, the gas should not continue to flow. It is a very good habit to get into to turn the petcocks off. One should rely on the float in the carb to completely seal off the flow of gas. Floats loose their buoyancy, debris gets into the system which can keep a float from properly sealing. If gas does get into the combustion chamber, you can develop a situation called hydraulic lock such that when you hit the starter button, the liquid won't compress and you end up with bent conrods. As a minimum, if the gas makes it to the oil sump, your oil won't be doing its job and you'll have the bearing surfaces failed in the bottom of the engine.

Kurt summed it all up pretty nicely...........

How much oil is being consumed as you ride?

How long does the smoke continue after lets say 10 miles of riding?

Do you park primarily or almost always on the sidestand?

Do you get fuel/gas on your boots when you ride?

Do you find a few drops of fuel on the ground after you park?

To me, each of the questions above tell different stories as to what is going on with your bike. Everything from you leaving the petcock on, just normal situation for "smoking" after sidestand parking, plugged carb overflow tubes, and on and on..........You have 2 different issues so let's figure them out......Dennis

Its been about 500-600 KM. smoke comes out of both exhaust. its worse when i start it, then it only happens when i push it hard. What i men't by the gas getting past the filter is once i turn off the bike and petcocks for the night there is still gas in the filters. The next day when i check on it there isn't any gas in the filters. they've poured into the carbs. could that be a problem? does it mean the petcocks aren't air tight?

I don't see anything wrong with hour your petcock or filters are behaving. But do get into the habit of turning off your petcocks...I do it for even short stops.

How much oil is being consumed as you ride?

didnt check just started my investigation and I'm at work

How long does the smoke continue after lets say 10 miles of riding?
it stops about a minute in.

Do you park primarily or almost always on the sidestand?

always on sidestand

Do you get fuel/gas on your boots when you ride?

no

Do you find a few drops of fuel on the ground after you park?

no

On stock carburetors, the float bowl has a brass tube that sticks up from the bottom of the bowl. This is an over-flow tube that is supposed to allow fuel to drip out of the bottom of the float bowl if the float/needle/seat fail to stop the gravity fuel pump from over filling the carburetor. The height of the tube is placed so as to divert an overflow from draining in to the carb throat and on in to the cylinder.

Bing's alcohol free float conversion does not have this overflow tube.

I just removed the cylinders for an unrelated reason but found the reason for my left cylinder smoke on start up--all 3 ring gaps managed to line up and position themselves at the bottom cylinder. Since you get smoke on both sides I don't think this is it--but maybe?????? It will tend to be the left cylinder for those, like me, who use the side stand all the time.

515PHOTO said:

I just removed the cylinders for an unrelated reason but found the reason for my left cylinder smoke on start up--all 3 ring gaps managed to line up and position themselves at the bottom cylinder. Since you get smoke on both sides I don't think this is it--but maybe?????? It will tend to be the left cylinder for those, like me, who use the side stand all the time.

Click to expand...

You can help the situation by slightly leaning the bike to the right for a short period of time after you've shut the bike down. This will let any residual oil drain back into the sump. I don't believe that the level of the oil in the sump is high enough that, even with the bike on the side stand, the oil will literally run out of the sump into the left cylinder.

I always thought white smoke is more water related like in colder damp climates. I get this always when I start the motor in the morning at the Sipapu, NM rally when it is in the forties and fog is still hanging around. Some condensation built-up by moisture in the muffler and condensation when the hot exhaust meets the cold moist ambient air.

I always thought burning oil gives a more blackish color. But who knows, I am not a mechanic, just riding...

/Guenther

Burning oil is bluish white, pure white is water, black is a rich fuel burn.

Wow thanks for all the replies guys.
Is it possible to have water come out after a couple of miles?

twisted, let me ask a different question:

Does the white smoke ever stop even after a longer ride?

/Guenther

the smoke only last's for the first 20 seconds after startup. but when i push it hard and stop my buddy says there's smoke.

Sounds not like an alarming situation to me as long as the smoke is pure white. Heh, you're riding an airhead - there can't be that much water in it.

/Guenther

For me, I am more concerned about your fuel/carb situation than I am a bit of condensation burn-off.......How many of us on a cool morning or even warm, have seen a bit of "smoke" come out on start up of any combustion engine?........Most autos will even drip fluid out of the end of the tailpipe. NO BIG DEAL

When one kills the engine and turns off the petcock, the fuel consumption of the engine ceases. Fuel should not disappear from the fuel lines as it sits for how ever long. Have you ever just reached down and rubbed your fingertips across the bottom of the carb bowl? Clean? Damp with fuel?..........We discussed the overflow tube above. Is it clean and working? Is the needle doing it's job?...........That fuel is going somewhere.....Good luck......Dennis

Check that your crankcase vent is working properly. Located on the rear upper portion of the engine just to the right of the starter. If this isn't working properly then it can cause oil to go into the intakes rather than flowing back into the engine. This valve is supposed to just let the vapours pass into the filter area, not the oil itself. This is more noticeable if you are getting more smoke out of the right side exhaust and will happen at other times than startup.

Parking these bikes on the sidestand is going to make the engine smoke some and if you find that the gas has left the filters after you've shut the petcock off, likely the floats or needle & seat are not shutting off the fuel. If all of the float stuff is working properly, gas should stay in the filters.

White smoke can also be condensation and the gas these days seems to contribute to this. Normally this will go away fairly quickly. Oil smoke is normally blue. I've seen the odd airhead just belch a huge clowd of white smoke on startup, on a warm bike, and the bike runs fine and uses no oil, so who knows whats up. If you have a habit of reving the bike up before shutting it off you are putting raw gas into the cylinders. That will also causing smoking at startup.

I had a R75/6 and sometimes it would smoke and other times it wouldn't. It even did the white startup smoke once. Carbs were all redone, new floats etc no black smoke at all. It was always better if I parked it on the centerstand if I was on a concrete surface, like the garage. A certain amount of smoke on startup is common on these year bikes. I had a 2000 R1100R that wouild also smoke the odd time at startup but put 6000 miles on a trip and didn't have to add any oil. Never caused any issues.