Topic: smokey breather & loud......but she finally started and runs

[greenjeans]

1972  CB750K

Finally got the project to run!!!  A tip for you guys....after Two-tired kept repeating in my previuos inquiries:
"make absolutely sure the carbs and every oriface is sparkling clean"   If your cabs have been sitting for over 10 years w/ stale dried up gas and varnish clean them and then clean them again, and once more for good measure.  I had mine completely apart and cleaned TWICE before everything smoothed out.  I thought they were clean the first time.

Anyway, a recap:  new oil and filter, cleaned out oil pan and oil pump - no metal in there - good sign.  Carbs cleaned, recleaned new jets, needles and gaskets.  New points and condensors.  tightened cam chain, adjusted tappets, set timing.

Anyway, it fires right up - I set the idle to about 2500 until it's warmed up, let the choke off and then idle it back down to about 1800.  There are some exhaust leaks, mainley around the collars etc - I have some exhaust gaskets that will go in there soon.  Let it run for 10 minutes or so...pipes don't seem to be smoking, all pipes temperatures seem to be reasonably close. 

Here are my concerns:

1. after it's good and warmed up, it smokes pretty steadily from the breather tube out of the top of the valves as well as
the engine...doesn't look like it's coming from any gasket surfaces, and I'm sure some of it is exhaust leakage, but it seems excessive.  Smokes even after it has been shut off like it's HOT.   It hasn't been run in at least 10 years so I'm sure it's just burning off junk etc...but it's a bit alarming, maybe I'm just paranoid.    Any ideas /

2. The engine itself seems noisier than it should be...like the cam chain or maybe the clutch basket ?  I have adjusted the timing chain already.   Probably a good idea to do it again since it's been running ?  I have also taken the adjuster apart and cleaned it.  I'm going to try and post a video later - hopefully it will be able to let you hear it.

3.  I'd be suprised if the rings weren't a bit sticky after all these years - Any suggestions there ? 
   I want to ride it around for a month or so before I blow it apart for paint etc.

4. Would you mess with any kind of oil treatment/cleaner (to clean sludge etc) and running again, then chaning oil again ?   
    Perhaps some Seafoam or something similar in the oil ?
    I'm going to be taking the clutch plates out to make sure they aren't stuck etc...

[andy750]

I cant answer all your questions but....for smoky breather - check your oil level....maybe too high? But best way to be really sure is to take it for a run....if you can....couple of miles should do the trick...if its STILL smokes after this then you may have a more serious problem. Likely (hopefully) its just due to not being run for so long. You can also take a tappet cover off and start engine and make sure oil is getting to the head!

BTW check the valve clearances again - if you havent done it before its best to do it at least twice..just to make sure you have them spot on. This can also be a noise source....tap, tap, tap.....

To give you an idea of a noisy cam chain listen to my 72 750....

http://s141.photobucket.com/albums/r58/andy750/?action=view&current=P1090240.flv

Engine itself is fine and bike runs great but camchain needs adjusting and you can hear this in the video. Yours may sound similar to this? To see if its the clutch instead pull in the clutch lever when its running - does the noise go away?

Good luck and sounds like you are getting there.

[TwoTired]

About breather "smoke":
The sources can be:
1. - water vapor -  Just like condensation forms on the outside of a cold drinking glass, so does condensation happen inside the engine.  The water is drawn from the atmosphere and deposited on the internal walls.  When the engine/oil is hot the water turns to vapor and exits the breather tube.  It will continue to do so as long as there is enough heat to make the vapor or until all the water is gone.

2 - Combustion blow by past the rings.  Stuck rings in the piston grooves can make this severe.  At higher RPMs, some bikes make so much pressure in the crankcase that it start pushing engine oil out the breather.
Naturally, combustion gases are hot and may vaporize the engine oil.

3. Oil vapor.  Oil on the backs of the piston crown can get hot enough to vaporize.

Water vapor is white is appearance.  Oil vapor usually has a bluish tint.  It's possible to have both at the same time.

About the noise:
I don't hear any noise.   
But, if you isolate the noise source it might help to diagnose.  Get a long screwdriver, and put the handle end in your ear.  Place the screwdriver tip on suspected sources of the noise.  The sound will telegraph up the screwdriver shaft and sound louder when you place the tip near the source of the noise that concerns you.

Sticky rings can shake themselves loose simply by running them at normal temps with good clean oil.  Assuming you don't have a scorched piston(s) with lots of burned deposits gluing the rings in the grooves.  If you do, then oil smoke out the exhaust is a telltale.
In cars, I've used Marvel Mystery oil to loosen up sticky thing inside the engine.  I think it has a high detergent action.  Never tried it on a MC engine, though.

I hate to ask... but what oil do you have in the engine now?

Cheers,

[greenjeans]

TwoTired, Right now it has Castrol 10w-30.  It's what I had on hand and what the manual I have suggests (But, that advice is 30 yrs old - I know motor oils have changed)   ** I just noticed that castrol makes an 10-30 "for motorcycles" so I'm going to try that or some Rotella (just finished reading some oil threads....) after I've run it a few more times.  I'll try some of that Mystery Oil to loosen / clean thing up as well.  There are also those additives that you add before changing the oil to help dissolve sludge etc...think that's worth a try ?

Would it be a bad idea to squirt something into each spark plug hole, 1 at a time while running  to help free up the rings a bit  ?
I'm assuming that they are a bit sticky after sitting all these years.  I have some Seafoam spray, WD-40, PB BLaster, brake cleaner, carb cleaner etc....

I drained everything and had the oil pan off, so hopefull I have the correct oil level in there.  There's no other places water could hide is there?  I keep it garaged and didn't find any evidence of water in the oil I drained out. I just put in what the capacity said in the manual.

Andy - thanks for the video....I think mine sounds similar.  I'll get one posted this evening so you guys can hear it.
I still need to take the clutch discs out and make sure they aren't stuck together etc before I can spin it around the block a few times.    I'll go ahead and check the chain and tappets again...couldn't hurt.   Oil level should be good and I've eye-balled the tappets -everything looks well oiled in there.

[TwoTired]

If you've looked inside the engine and didn't find a sludge coating, then why would you need a sludge remover?  And, if you did have sludge, it would come off in sheets with a high detergent oil and clog up the oil screen.  This would be bad.

Just run the bike and change the oil after it has been thrashed a bit.  The rings will either un-stick, (if indeed they are sticking), or they won't, with some time on the engine.  Running under load helps, as the combustion pressures can get behind the rings and break them loose.  Just don't run it so hot that the oil turns to glue.

You have to have a lot of water in the oil for it to show visible signs.  The condensate that occurs inside, combines into the oil like an emulsion when it's thrashed about.  If you have enough, it starts to look like brown mayo.  All engines get water in the oil from condensation.  If your air has humidity, it has water in it.  It doesn't have to smack you in face for you realize it's there.  The vapor out the breather pretty much proves you have some.  It will normally stop once you have about 15 minutes run time at full operating temperature.

Water can and does hide and cling to the inside walls of your engine, provided you live on this planet in an area that gets rain in its atmosphere.  Water condenses on the inside of your engine every time the engine cools down in temperature, this includes when the engine isn't even run, as the daily temps climb during the day and fall during the night, so does your engine temp.

Cheers,