White smoke on startup

WEM

WEM

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Dec 8, 2017
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My 1974 850 MK II Commando has recently developed a new issue. Immediately on starting, significant white smoke comes out the drive side exhaust pipe. No smoke at all from the timing side. This has only started happening in the last two weeks or so. The smoke clears after 2 or 3 minutes and no sign of any smoke thereafter. The bike is running well and starts on the first kick. (Not sure if it’s related at all, but the drive side cylinder has always run a little richer than the timing side based on the colour of the plugs, despite frequent adjustment of the carbs to try and address the situation.) Based on a little research of previous threads, it seems possible issues might be something like a defective valve seal or a blocked oil drain hole. Any and all advice/suggestions appreciated.
 
Pull the intake valve cover and see if the valve seal has moved up to the retainer. It can happen. You may be able to push it back down. Although I'm not sure if that is possible with dual springs. Maybe one of the guys with a stock spring setup can elaborate on whether or not the seal can be pushed back down. With single beehive springs it can be. Chances are if that seal is really old it is not working too well and possibly hard as solid plastic.

Running ultra rich would produce black smoke, so it's not the richer running issue if it is running good otherwise. I can think of other things, but they are too negative to be the cause without a noticeable loss of power.
 
What Schwany said. Also, don't park the bike on the side stand if you are. The drive side of the intake area always has more oil - if you shut it off on the side stand or put it in the side stand right after shutting it off and you have a bad valve seal, the drive-side intake valve can get oily and possibly even that cylinder.
 
When my MKII 850 left side started to give puffs of smoke (grey or whitish), is was mostly immediately after a quick throttle blip (as rpm came back down). Turned out to be embrittled, cracked & crumbly valve seal. Replaced both intake seals with head still on engine in bike using Ludwig's method and his tool.

To check if rocker box not draining, remove cover and tip in some warm/heated oil, monitor how long it takes to drain (bike on CS, level). Try running some wire down the small drain hole just at the edge of the timing side valve spring seat (hard to see). I did this and got the wire all the way down to the base of cylinder where it makes a 90 deg bend. Also managed to spray some WD-40 with the straw down there. This gave faster draining when next checked.
 
Yup , it's a bad embrittled oil seal on the intake for sure.
Time to order in improved teflon seals for the intake valves. Very pleased with this type , not plastic .
 
Tornado said:
When my MKII 850 left side started to give puffs of smoke (grey or whitish), is was mostly immediately after a quick throttle blip (as rpm came back down). Turned out to be embrittled, cracked & crumbly valve seal. Replaced both intake seals with head still on engine in bike using Ludwig's method and his tool.

To check if rocker box not draining, remove cover and tip in some warm/heated oil, monitor how long it takes to drain (bike on CS, level). Try running some wire down the small drain hole just at the edge of the timing side valve spring seat (hard to see). I did this and got the wire all the way down to the base of cylinder where it makes a 90 deg bend. Also managed to spray some WD-40 with the straw down there. This gave faster draining when next checked.
Click to expand...
Thanks to everyone for the suggestions. Looks like faulty valve seal is the consensus.
Any recommendations on which valve seals are the best? A little research shows there are a lot of choices. And any direction on where I can find info on Ludwig’s method? Thanks.
 
WEM said:
Thanks to everyone for the suggestions. Looks like faulty valve seal is the consensus.
Any recommendations on which valve seals are the best? A little research shows there are a lot of choices. And any direction on where I can find info on Ludwig’s method? Thanks.
Click to expand...
See my post on this thread and the pdf from Ludwig I attached:

Post in thread 'Replacing Valve Stem Seals (in situ) Pitfalls?' https://www.accessnorton.com/Norton...stem-seals-in-situ-pitfalls.35061/post-576640
 
WEM said:
Thanks to everyone for the suggestions. Looks like faulty valve seal is the consensus.
Any recommendations on which valve seals are the best? A little research shows there are a lot of choices. And any direction on where I can find info on Ludwig’s method? Thanks.
Click to expand...
www.accessnorton.com

Valve seal Recommendation(s)

Looking for manufacture(s) and part numbers for intake valve seals for a '71 750 with bronze guides. The seals that came in the "genuine gasket and seal kit" are a serious joke. Best.
www.accessnorton.com www.accessnorton.com

Teflon seals and valve stem wear

The buzz is that viton valve seals work better for street use whereas teflon seals seal too well and can dry up the stems resulting in accellerated wear. What have high milage Norton owners found? viton seals (easy to install) teflon seals (require installation tool)
www.accessnorton.com www.accessnorton.com
 
If its parked on the sidestand , oils on the drive side .

If its warm , does it do it .
Is it just wet sumping , oil in left of the head .
 
I had left side smoke and left dirty plug. I solved it by cleaning the drain with a guitar bottom E string, which I could reach through the rear cover. It was part blocked with Wellseal.
 
You really want to see the first year of BMW K series bikes with the head side leaning on the side stand .
White Atom bomb on start up.
Now that's smokin'.
Head was flipped over to the other side after . Problem solved.
Lesson: pooling head oil is a no good.
 
Torontonian said:
Thought it was.
Click to expand...


Torontonian said:
How did BMW stop the atom bomb startup ?
Click to expand...

It never really was completely cured although I believe there was a change made to the piston rings but one gets into the habit of using the centre stand when the K is parked for any length of time as I do.

www.k100-forum.com

Smoking at startup

Hi guys, I'm General John. I'm new here and greetings from South Africa! I have a K100RS 1988 that was standing for a while. So, when I fire her up, it's just s
www.k100-forum.com www.k100-forum.com
 
Last edited:
It’s been awhile since I last posted to this thread regarding smoke from the left exhaust of my 1974 850 MK II on start up. Consensus of members at that time was that it was likely a bad valve seal but that a blocked drain hole in the inlet valve cavity was also a possibility. I am finally getting around to this project and before removing the head to access the valve seals I removed the inlet valve cover and had a look. I’m not sure how much oil, if any, should be pooled in the bottom of the inlet valve chamber but there is more there than I would have expected to see. I’m going to try and get a wire down into the drain hole to see if the oil drains. I guess my question is if the drain hole is plugged or partially plugged and oil is pooling in the inlet valve chamber, why would smoke come from the left exhaust only. Shouldn’t both exhausts smoke? The bike is always parked on the center stand.
 
WEM said:
It’s been awhile since I last posted to this thread regarding smoke from the left exhaust of my 1974 850 MK II on start up. Consensus of members at that time was that it was likely a bad valve seal but that a blocked drain hole in the inlet valve cavity was also a possibility. I am finally getting around to this project and before removing the head to access the valve seals I removed the inlet valve cover and had a look. I’m not sure how much oil, if any, should be pooled in the bottom of the inlet valve chamber but there is more there than I would have expected to see. I’m going to try and get a wire down into the drain hole to see if the oil drains. I guess my question is if the drain hole is plugged or partially plugged and oil is pooling in the inlet valve chamber, why would smoke come from the left exhaust only. Shouldn’t both exhausts smoke? The bike is always parked on the center stand.
Click to expand...
Could be because the left seal is more worn out than the right or the guide is looser. There are differences in the running temps between left/right for unexplained reasons, etc.

I managed to get a long (maybe 10-15cm) bendy straw from a can of SeaFoam carb spray into the drain hole and give it some blasts of WD-40 or Brake Cleaner. Note whatever you put down there ends up in the timingchest and will contaminate the engine oil so don't go too crazy, change oil shortly afterwards etc. Can of compressed air might work as well.

You can pour in a set amount of warmed oil into the rocker box and watch how fast it drains. Then clean and check again to see if you've improved. Note when running the engine case pressure pulses will help suck oil down that hole so it's not an accurate check.
 
WEM said:
It’s been awhile since I last posted to this thread regarding smoke from the left exhaust of my 1974 850 MK II on start up. Consensus of members at that time was that it was likely a bad valve seal but that a blocked drain hole in the inlet valve cavity was also a possibility. I am finally getting around to this project and before removing the head to access the valve seals I removed the inlet valve cover and had a look. I’m not sure how much oil, if any, should be pooled in the bottom of the inlet valve chamber but there is more there than I would have expected to see. I’m going to try and get a wire down into the drain hole to see if the oil drains. I guess my question is if the drain hole is plugged or partially plugged and oil is pooling in the inlet valve chamber, why would smoke come from the left exhaust only. Shouldn’t both exhausts smoke? The bike is always parked on the center stand.
Click to expand...
On the center stand there should be only a little but still slightly more on the left. Just dump about a 1/2 cup of oil in the intake and see if it goes down to where it is now. The drain is the only way out unless way out. BTW, some center stands lean a little one way or the other.

If it is truly white smoke (not bluish white) and goes away after running a little, then it might be water in the left carb. The pilot (idle) circuit starts near the bottom of the bowl so any water collected there will go through the engine and make white smoke. How does it get there and not in the right? Several weird possibilities.

If it's truly white smoke and only just after starting - I would ignore it once I'm sure my oil drain in the intake is open.
 
I'd pull the head and fit new telflon valve seals and have a machine shop check/replace guides if necessary .
 
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