Topic: white smoke from breather tube? (1977 CB550K)

[seeaaannnn]

Hey all,

First post here.  Glad I found the community. 

I just bought a 1977 CB550K a couple weeks back.  Still new to these old bikes.  Its in great shape; 7300 original miles, clean engine, clean tank, etc.  Just cleaned carbs, checked points, timing and all that.   The only issue with the bike thus far is it idles VERY high when completely warm, like 3500rpm.  I just got home from a ride and adjusted the idle screw to about 1500rpm.  I noticed near the end of my 30 minute ride that there was a lot of white smoke coming from the breather tube(?).  Its the tube coming from the top of the engine and stops in between the carbs.  Smelled a little like gas.  Can anybody tell me what it is from?  I can only think the engine was overheating due to high idle speed.  Video attached:

https://www.youtube.com/watch?v=sGrYkyweoIM

I'm stumped.  thanks for the help!

[Deltarider]

Runs like a dream IMO. Try to find out what the true RPM is with a known accurate tachometer. I once had to adjust a K3 at 1700 rpm on it's tachometer to get a 1200 true idle.
Some white smoke from the breather is not abnormal, especially if the bike has done short rides and there's condense in the oil. The breather is there to get rid of socalled blow-by gasses.
But with so few miles on the odometer I wouldn't worry. Can't believe that so regular bikes show up in this forum with so little miles. Why did people buy them? To look at them? Did they get scared to ride them? Would like to buy it from you and tour the US once more.

[seeaaannnn]

Runs like a dream IMO. Try to find out what the true RPM is with a known accurate tachometer. I once had to adjust a K3 at 1700 rpm on it's tachometer to get a 1200 true idle.
Some white smoke from the breather is not abnormal, especially if the bike has done short rides and there's condense in the oil. The breather is there to get rid of socalled blow-by gasses.
But with so few miles on the odometer I wouldn't worry. Can't believe that so regular bikes show up in this forum with so little miles. Why did people buy them? To look at them? Did they get scared to ride them? Would like to buy it from you and tour the US once more.

Yup, its a great bike.  I got really lucky in that its one of those situations that vintage bike lovers are always looking for.  The bike came from Arizona where the air is dry and it never rains.  Some older gentleman apparently bought the bike and kept it in his garage for years, but still started it up and rode it around once in a while.  The bike is very clean with a few rust spots on the swing arm, and around the chrome on the tank.  Its hard to start cold, but once its running its like a new bike.  It surprised me with its handling and pull for such an old bike... will be keeping this thing for years.

Speaking of cold start, is there a special technique with these hondas?  I usually pull out the choke, set fuel on reserve, crack the throttle a wee bit, and use the electric starter.  Usually takes a few tries to get the engine to turn over.  Sometimes I have to rock the throttle back and forth between open and closed.  Once the engine turns, I really need to open the throttle with the choke out for about 30 seconds, then push the choke back in.  I'll keep the RPMs at about 2.5k for about a minute and check idle speed.  Once I'm around 1500, I ride off.  Just checking to see if there's a better way.  Makes me nervous keeping the choke open so long and rocking the throttle... don't want to flood the engine.

[goldarrow]

bike sounds and looks great.  just ride the snot out of it!

[Deltarider]

K3s were equipped with carbs that were designed to run leaner. The choke was combined with a device that opens the throttle somewhat like in cars. It's the only model that you ride with the knob still a bit pulled out for the first yards.
Older 550 models with old style carbs (choke operated from the side) you can close (I mean: open) the chokes before you even start riding as long as you yourself help by keeping the throttle somewhat above idle. I'm not sure about the F2s though. Maybe theý have to be treated liked the K3.

just ride the snot out of it!

Yes, but not before the bike is well warmed up. If not you can expect oil leaks.
So take it easy the first 6-7 miles. When well warm you can subject the engine to anything you want.
I recommend to avoid short rides. Often I get the impression overthere these bikes are used for transport from one side of the city to the other. Use a moped, a scooter or a pedal bike for that.
Make a long ride and then check if there's still white smoke coming from the breather tube. You'll always see some white smoke though but little. Or change the oil if you'haven't done that already.

[seeaaannnn]

bike sounds and looks great.  just ride the snot out of it!

Thanks!  I plan on it 

[seeaaannnn]

K3s were special and designed to run leaner. Their choke was combined with a device that opens the throttle somewhat. It's the only model that you ride with the knob still a bit pulled out for the first yards.
Older 550 models with old style carbs (choke operated from the side) you can close (I mean: open) the chokes before you even start riding as long as you yourself help by keeping the throttle somewhat above idle. I'm not sure about the F2s though. Maybe theý have to be treated liked the K3.

Hmmmm interesting.  I have a K3.  I usually ride into first gear with the choke knob pulled out on a cold start.  After shifting into second ill push the knob in, and things are good from there.   Thanks for the info, I've heard the K3 models have a different carb/choke setup, so its good to get conformation. 

[TwoTired]

Once you tweak the main idle knob for correct idle speed you never need to touch it again.

The choke is coupled to a fast idle cam which rides on a separate adjustment screw, or fast idle speed adjust.

The process is to use choke for starting and regulate the knob position to control a fast idle speed, until the bike is warmed up and the choke knob can then be push in all the way.

The K3 is very sensitive to adjustments during cold operation.  Before you tweak anything else, make certain you have recently completed the 3K tune up checklist as well as a good vacuum sync.  I'd also use a brand new stock air filter for the baseline tune process, and verify the breather system is clean/clear, and has all the proper drain and vent tubing connected.

Far better to have the D7EA heat range plugs installed.