Topic: Smoke from blow by, smoke in one exhaust pipe - thoughts?

[Tretnine]

I've got smoke coming out of #2 and a fair amount of smoke coming from the blow by. Low mileage motor (11k) cb550k -1978. All tuning is done. Ideas?

[75cb550 (kyle)]

white/blue smoke? smell like oil?

[Tretnine]

white, sorry. It's definitely not water vapor. Will idle between 1,000-1,200 but it gets... clunky. And yes, syncing has been done, and redone. Smoke has started to come out of some, if not all, of the other pipes. I've done the maintenance, but I don't know what the previous owner has done to this thing in addition to not tightening the valve cover tight enough.

Brady

[motorhead55]

Sounds like a compression check is in order. Excessive blowby can be from a burnt piston or broken rings.

[75cb550 (kyle)]

hmm...  rings? low mileage though...

[Caymen]

Bike is 32 years old. My guess it is valve stem seals and/or guides.

Mine is doing the same thing. It doesn't always smoke. Some times it smokes bad and then sometimes not at all. It could be one cylinder, all of them, somewhere in between, or none. Sometimes light smoke, sometimes awful smoke.

Compression between all 4 cylinders is within 5% of each other and the engine runs great.

I think my issue is the valve stem seals and/or guides. Plan to replace in the fall.


Tom

[TwoTired]

I've got smoke coming out of #2 and a fair amount of smoke coming from the blow by. Low mileage motor (11k) cb550k -1978. All tuning is done. Ideas?

How long has the engine been at full operating temperature?

White smoke is water vapor, like clouds.  Takes a while to vaporize all the internal condensation in pipes and engine with heat, especially into high humidity atmospheres.  Now, when it gets blue-ish you have oil burning.  If black-ish you have unburned hydrocarbons.

[Tretnine]

I've got smoke coming out of #2 and a fair amount of smoke coming from the blow by. Low mileage motor (11k) cb550k -1978. All tuning is done. Ideas?

How long has the engine been at full operating temperature?

White smoke is water vapor, like clouds.  Takes a while to vaporize all the internal condensation in pipes and engine with heat, especially into high humidity atmospheres.  Now, when it gets blue-ish you have oil burning.  If black-ish you have unburned hydrocarbons.

Could it be an improperly torqued head gasket?

I put 50 miles on it this weekend over a couple of hours, I don't think it's vapor at all. It's also pretty erratic. The warmer the motor gets the higher the more smoke I seem to get. Smoke is also erratic, sometimes it's here, sometimes it's there, sometimes it's everywhere, but always comes out of the blow by when engine is up to temp. Compression at last check was 90 90 80 90. It's a bit embarrasing in traffic and the idle is a bit... chunky, not terrible, just a bit not right.

I've been having lots of oil leak problems, both from the bottom and top. Oil is burning off the pipes, but there is definitely oil coming out of the pipes, also.

[TwoTired]

Every time the engine cools down, moisture in the air condenses on the inside of the pipes and engine.
It takes a little while, and some sustained heat, to vaporize the condensate.

If it is smoking after the water has vaporized, then you are burning oil and the smoke should have a bluish tint.

Are all the head pipes getting even heat? Idle and mid throttle?
Spark plug deposits?

[camelman]

I had the same thing with my 350F.  I had lots of white smoke coming out of engine blowby hose.  It was worse after the engine was well warmed up, so I know it wasn't water vapor (I couldn't have that much water vapor in there after three or four hours of riding).  I did notice that not as much blowby was generated at higher RPMs.  I pulled me engine apart to replace the valve seals, and they were hard as plastic.  I haven't started it back up yet, but I recommend replacing those seals.

[Tretnine]

I had the same thing with my 350F.  I had lots of white smoke coming out of engine blowby hose.  It was worse after the engine was well warmed up, so I know it wasn't water vapor (I couldn't have that much water vapor in there after three or four hours of riding).  I did notice that not as much blowby was generated at higher RPMs.  I pulled me engine apart to replace the valve seals, and they were hard as plastic.  I haven't started it back up yet, but I recommend replacing those seals.

This sounds exactly like what's happening to me. you going to fire that bike up soon? I'm interested to see if it fixed your problem.

[camelman]

Hopefully in the next couple of days.  I need to clean and repaint it first.  I'll let you know.

[seaweb11]

72 CL350 same issues yesterday.
Oil was leaking out the tube at stops, at the end of a very long hot run it was smoking blue and had a gas / oil smell. Once it cooled off it went away.

Can you check the carb overflow function while carbs are on the bike?

On the 750s you just loosen the screw and gas comes out the overflow tube. On the CL350 when I loosen the screw gas comes out the screw hole.


Have I mentioned I HATE working on this 350!

[camelman]

My valve guide seals fixed the issue.

I noticed something else the other day on a CB500F.  The idle jet came loose in one carb and fell into the bowl.  Massive amounts of fuel poured into the cylinder and flooded it out, but not before filling up that exhaust pipe (4 into 4) with lots of fuel.  I realized I was standing in a spraying cloud of fuel, so I turned the engine off.
I fixed that carb, but then it happened to the carb next to it too.  So, both #1 and #2 pipes were filled with fuel.  I let it sit a day and then started it.  It took about twenty minutes for all of the fuel to clean out of the pipes.  They blew white smoke while they were cleaning out.  If you happen to have a lot of raw fuel going through any one cylinder (which could be part of the reason for the clunky idle), then the white smoke coming out might be from that raw fuel blowing out of the exhaust.

Camelman

[bobjohnson]

My valve guide seals fixed the issue.

I noticed something else the other day on a CB500F.  The idle jet came loose in one carb and fell into the bowl.  Massive amounts of fuel poured into the cylinder and flooded it out, but not before filling up that exhaust pipe (4 into 4) with lots of fuel.  I realized I was standing in a spraying cloud of fuel, so I turned the engine off.
I fixed that carb, but then it happened to the carb next to it too.  So, both #1 and #2 pipes were filled with fuel.  I let it sit a day and then started it.  It took about twenty minutes for all of the fuel to clean out of the pipes.  They blew white smoke while they were cleaning out.  If you happen to have a lot of raw fuel going through any one cylinder (which could be part of the reason for the clunky idle), then the white smoke coming out might be from that raw fuel blowing out of the exhaust.

Camelman

Yep, the other thing could be fuel in the oil. As the oil heats up and gets kicked around in the crank case, the fuel vaporizes out of it, leading to white smoke out of the blow by. It will smell like running super rich but without the black smoke.

[TwoTired]

FYI,
Honda never made a CB500F.

F models in that class were all CB550 F Super Sport and they all had 4 in 1 exhaust.