Topic: smoke coming out of crankcase breather tube

[tdtravis80]

Hello, I need some help/ideas so hopefully someone here can help a brother out. I tore my engine apart to replace gaskets because it was leaking oil. I relaped valves and replaced all the gaskets I could and put it back together. Got it running and then I started having an issue with a steady stream of smoke coming out of my crankcase breather tube after the engine warms up. So I researched up on what could cause this and came up with that is due to excessive pressure in the crankcase due to bad valve stem seals, bad piston rings, lack of oil (which is not the case) and or it could also be a bad oil pump (not very common). rode it too long this way and I ended up blowing the head gasket. So I tore my engine apart again and replaced the valve stem seals and piston rings and honed the cylinders (I checked my compression before I tore it apart and compression was good but I replaced them anyway). I checked all my tolerances and everything came out good including the cylinder head which I was worried about since the head gasket blew. So I put it back together and I'm still having the same issue. I thought it might be a bad oil pump so I went and bought an oil pressure gauge. Plugged it in and ran the bike at 3,000 rpms like my manual says to do and I got just above 60 psi and that is what my manual says it should be. The engine seems to be running hotter than it should be and I'm not sure why. I'm running out of ideas and hopefully someone here has sogive me other ideas that I can check out. Sorry for the long post! Thanks for any information you can me! Travis

[ADW]

Go actually RIDE the thing for a while and I'll betcha the "smoke" disappears. It's probably just condensation from the engine being opened up. Once you get 'er hot and run it for a while I bet it goes away. (I had the same concern when I got my new-to-me 350F. There was "smoke" coming out the breather. But once I went out and got the thing to operating temperature and ran her for an hour it was gone. And that was 2 years ago and the bike hasn't done it since and runs perfect.)

[kghost]

Did you hone the cylinders when you put the new rings in?

They tend to glaze after running a while which is. Fine if they match the old rings.....

As mentioned ride it a bit. Takes a while for the rings to seat in anyways.

[Vincent P]

NOT SAYING THIS IS YOUR ISSUE but check out some of my earlier posts:

http://forums.sohc4.net/index.php?topic=121715.msg1378386#msg1378386

I had an incredible amount of smoke coming from the breather tube. I replaced the head gasket and it ran fine for an hour or so then the smoke would start; think white smoke coming from a stunt plane at an air show. Like you I had the cylinder head reworked with new valves, seals and machining; piston rings in good order and so forth. During assembly I torqued the head down, I let it sit for 24hrs and repeated the process. Great compression when tested after the initial assembly and before running (cranked motor and tested).

Replaced the head gasket twice with the same issue.

Note: at first I thought it was excessive crankcase pressure do to oil coming out the breather hose from the oil tank...

Cause: #2 sleeve dropped almost 2mm so I did not have a flat sealing surface between the jugs and the head. I had great compression and performance until the slight gap coupled with the compression from the cylinder blew the gasket out; let me state it does not take long to happen.

ADW suggests go for a ride; if you do stop regularly because when I did it spewed oil all over my rear tire at high RPM from the rocker breather hose and oil tank breather.

Good luck.

[Vincent P]

Another though comes to mind; how much oil are you putting into the motor, over filling will cause this issue also.

Remove the spark plugs and look to see if there is any wetness or discoloration due to oil on any of them.

Lastly, if you throttle the bike, do you have any smoke from the exhaust?

[tdtravis80]

Go actually RIDE the thing for a while and I'll betcha the "smoke" disappears. It's probably just condensation from the engine being opened up. Once you get 'er hot and run it for a while I bet it goes away. (I had the same concern when I got my new-to-me 350F. There was "smoke" coming out the breather. But once I went out and got the thing to operating temperature and ran her for an hour it was gone. And that was 2 years ago and the bike hasn't done it since and runs perfect.)

The smoke actually appears after the bike warms up and gets hot so I don't think it is condensation

[tdtravis80]

Did you hone the cylinders when you put the new rings in?

They tend to glaze after running a while which is. Fine if they match the old rings.....

As mentioned ride it a bit. Takes a while for the rings to seat in anyways.

Yes I did hone the cylinders out with a honing stone.

[tdtravis80]

Another though comes to mind; how much oil are you putting into the motor, over filling will cause this issue also.

Remove the spark plugs and look to see if there is any wetness or discoloration due to oil on any of them.

Lastly, if you throttle the bike, do you have any smoke from the exhaust?

I put about 3.2 quarts of oil in the bike like the manual says to do.  I did remove the spark plugs and they were dry with a slight grayish bluish tint to them.  There is really only smoke that comes out of the exhaust when I start it up from not running it in awhile but when she warms up there isn't much if any smoke coming out of the exhaust.

[Vincent P]

If you throttle the bike, do you get a steady stream coming from the vent?

I know with the issue I had, throttling it caused more smoke to spew.

If you ride it are you noticing any drop in performance or power; also when you did the compression test, what readings did you get from the gauge, and was there one cylinder lower than the rest?

[tdtravis80]

I 'm not sure if the smoke increases when I would twist the throttle. Though, after I would ride just for a little bit enough to get the engine hot there is a steady stream of white smoke coming from the crankcase breather tube. I did do a compression test and all cylinders checked out good and at around 145-150 psi. I don't notice any loss of power either though the engine seems to be running way hotter than it should be but I heard with bypass gas that the engine would be running hotter.  Before I tore my engine apart I did not ever have this problem.  When I tore it apart I noticed a striped bolt hole in the cylinder head so I ordered a new used one off ebay and installed it when I put it back together.  Everything checked out good with the new used cylinder head but I never checked the valve stems and stem guides to see if they were in tolerance.  So I'm wondering if the bypass gas could be getting threw there somehow though I have replaced the valve stem seals twice now.   I'm thinking about fixing that bolt hole on my original cylinder head and putting that back on. I mean could that possibly be my problem?  I don't think I've thanked you yet but thanks a lot for all of your knowledge and suggestions. It is greatly appreciated!!  Travis

[Vincent P]

I think all of us would say anytime as far as helping out goes.

Which bolt stripped on the head exactly?

[Magilla]

Take he bike for a long ride.  Not just one that heats up the motor.  I had this same issue last year and the good folks on this site suggest that I ride it.  They were right.  I took it for a nice 50+ mile ride and the smoke stopped.  It has never come back again.  And YES I did check to make sur ei still have oil in it.

[TwoTired]

The smoke actually appears after the bike warms up and gets hot so I don't think it is condensation

Really?
Boil some water on the stove.  When is it you see the white vapor coming from the pot?  Before or after it is heated?
Does the white vapor stop before all the water is gone?

Of course, if it was simple condensate vapor, it would mean you've taken the engine apart for nothing, how many times now?  And, it will still never be "fixed" until you thoroughly get the entire engine unit to operating temp and hold it for about 20 minutes.

Many never see that vapor because there is a factory engine breather unit that sends the vapor and other gasses into the combustion chamber.  Just saying.

Oil vapor has a blueish tint to it.  Lot's of piston ring blowby will usually turn the oil black in very short order.

[tdtravis80]

Another question I have is when you guys replace your paper gaskets do you use the tacky gasket sealer with paper gasket? Or do you use nothing? My experience with gasket sealer was it was hard to lay it down consistently there were definitely spots that were probably a little thicker than others due to that stuff being stringy, tacky and hard to work with. So I guess I'm wondering if that could be an issue.

[tdtravis80]

I think all of us would say anytime as far as helping out goes.

Which bolt stripped on the head exactly?

It was one of the bolts on the end. One of two allen bolts on the head

[tdtravis80]

The smoke actually appears after the bike warms up and gets hot so I don't think it is condensation

Really?
Boil some water on the stove.  When is it you see the white vapor coming from the pot?  Before or after it is heated?
Does the white vapor stop before all the water is gone?

Of course, if it was simple condensate vapor, it would mean you've taken the engine apart for nothing, how many times now?  And, it will still never be "fixed" until you thoroughly get the entire engine unit to operating temp and hold it for about 20 minutes.

Many never see that vapor because there is a factory engine breather unit that sends the vapor and other gasses into the combustion chamber.  Just saying.

Oil vapor has a blueish tint to it.  Lot's of piston ring blowby will usually turn the oil black in very short order.

Well, the first time I took it apart it was leaking oil and gaskets needed to be replaced.  The reason I took it apart the second time is because I blew the head gasket and I'm not sure the reason why it blew. I was thinking it had to do with the smoke coming out of the breather tube because I read in other forums that the smoke was due to excess pressure in the crankcase. Actually the smoke didn't start to appear till after a month of riding the bike. Then the smoke started to appear after I took it for about 150 mile trip and it would appear after the engine warmed up every ride after. Then the head gasket blew. So are you saying this smoke is normal? If it was condensation in the engine wouldn't it eventually go away? What would cause the head gasket to blow? The head and cylinders are not warped because I checked that and they were within .002 of an inch. I'm not a mechanic and don't claim to be one. I'm interested in taking care of my own motorcycles and being more self sufficient even if it cost me a little more in the beginning for the knowledge. If you need any information from me to help diagnose the problem let me know. I checked pretty much every tolerance I could think of except the valve stems and guides.  I appreciate all of the help guys!  Thanks, Travis

[TwoTired]

The reason I took it apart the second time is because I blew the head gasket and I'm not sure the reason why it blew.

Very unusual the head gasket blows on the stock engine.  These only have 9:1 compression ratio.  Either the head or block is warped, faulty torque sequence, using the wrong torque specs, or the cylinder filled with an incompressible liquid at some point.

I was thinking it had to do with the smoke coming out of the breather tube because I read in other forums that the smoke was due to excess pressure in the crankcase.

That would be blow by and leaking piston rings or the piston is too sloppy in the bore.  However, if the breather is working, very little pressure actually builds in the crankcase.  The exit tube will move a lot of air.   Any pressure is usually bled off nearly as fast as it builds.   Well, perhaps at 10000 RPM. 

Actually the smoke didn't start to appear till after a month of riding the bike. Then the smoke started to appear after I took it for about 150 mile trip and it would appear after the engine warmed up every ride after.

Still not clear if you are noting actual smoke (Particulates suspended, or water vapor).  Are you saying the "smoke" is still there after a 150 mile ride?
If there is any humidity in the atmosphere, each day of the earth's cool down cycle will cause condensation to form inside on the inside engine walls, whether the engine has run or not.  Ever see water form on the outside of a cold beverage glass?  Lowering the temp of water laden air, causes it to separate and deposit on the colder surfaces.

Then the head gasket blew. So are you saying this smoke is normal? [/quote]
White water vapor is pretty normal after each overnight's morning startup, oil smoke, not so much.  But, the latter smells of oil and is usually blueish.  Oil smoke also lingers much longer than water vapor.  But, this is dew point related.

If it was condensation in the engine wouldn't it eventually go away?
Should after 20minutes of operation beyond getting to full operating temperature.  There is some wiggle room here. and the trans case is also fed to the breather.  It has to get hot enough to vaporize water.

Have you told us what bike we are talking about?

[Vincent P]

I have to agree with TwoTired,

The more you post the more it sounds like what I had experienced a couple of months ago. My white smoke and it was smoke not condensations did not start right away, it started after the 3rd ride; my ride was to work and back which is a 30 mile trek. Realistically you could say when i was close to the 100 mile mark.

in the end it was as I stated, #2 cylinder sleeve had dropped which caused the head gasket not to seal properly, and the compression from the cylinder to blow out the gasket.

Don't know if you can see it in this picture.

[Vincent P]

Here is a shot of the second blown gasket.

[Vincent P]

I have to agree with TwoTired,

The more you post the more it sounds like what I had experienced a couple of months ago. My white smoke and it was smoke not condensations did not start right away, it started after the 3rd ride; my ride was to work and back which is a 30 mile trek. Realistically you could say when i was close to the 100 mile mark.

in the end it was as I stated, #2 cylinder sleeve had dropped which caused the head gasket not to seal properly, and the compression from the cylinder to blow out the gasket.

Don't know if you can see it in this picture.

look a the partial shot of number 2 sleeve in comparison to number 1 which is nice a flus; a bit hard to tell at the angle of the shot, but it has dropped.

[Vincent P]

Here is a much better pic.

[tdtravis80]

Sorry if I didn't mention it but my bike is a 1981 cb650.  So what I'm understanding is there's nothing wrong with my bike and I'm freaking out about nothing. No it wasn't smoking after 150 mile trip. I just started to notice it coming from the hose after that trip. Its not a bluish smoke its more white than anything. So from what you are telling me it must be condensation.   Like I said I took a dial indicator to head and block on a calibrated granite block and they were both within .002 of an inch all around. My clymer says its warped if it is out more than .010 of an inch.  I followed the torque sequence that was in the clymer and torqued them down to the specs they gave me with a snap on torque wrench. So as far as the head gasket blowing is a mystery to me too.  Maybe it could of been a bad gasket even though it was brand new? I now know I shouldn't have now but I did use the tacky gasket sealer with the paper gasket and its hard to lay that down evenly so I don't know if that could have been a contributor or not.   So the consensus is I'm good to ride right? Thanks again for your time! Travis

[tdtravis80]

Here is a much better pic.

My compression is good and I checked when I started to notice the white smoke before the gasket blew

[Vincent P]

Travis,

It sounds as though you have done a thorough inspection; at this point the only thing I can think of is the gasket material used. I've typically heard depending on the gasket used between the jugs and the head, you should not have to use any sealer or gasket coat on a typical gasket. I have seen some use copper coat on both sides (spray on type) letting it sit then installing.

Lastly, it does not mention this in most manuals, but a couple of YouTube videos I've watched and people I've spoken with have always stated that you torque the head down in a slow sequence, bringing it up to the final torque foot pounds; then let it sit for 24hrs and repeat the sequence.

Try going for the ride suggested taking it easy and checking (pull over periodically) to see if this resolves the issue; hopefully it does. Keep us posted...

[tdtravis80]

 I will start riding it and I  will  definitely  keep you  guys  posted.   Another question I have is how you guys go about breaking your engine in.  the second time I took the bike apart I replaced the rings and honed the cylinders so my manual says I have to break it in for 1500  miles.  what the manual says is ride it  for 500  miles at no more than 1/3  throttle varying the speed and change the oil every 500 miles.  That is how you were suppose to break it in back in 1981  just wondering if that has changed at all.  Thanks again for all your help guys!  You  have been great!  Travis