Topic: '74 CB550 Back with another problem. Smoky exhaust #1

[Jimsun]

Hey guys
I am at a stumped as to why my exhaust is still spitting out smoke.

I have fully done the 3k tune up followed by a vacuum synch. All of the other pipes except the first cyl exhaust are good.

I use stock spark plugs. I use 10w-40 mineral oil.

The bike has stock pipes, intake, points etc.

I have tried .5/1/1.5/2/2.5/3 turns out of my air screw.

Ill post a video of the pipes. Im posting this in advance in hopes that someone has had this issue with stuck set up.

Edit: my friends say the smoke is white.
Also note that i went from synthetic to mineral.

Heres the Video

https://www.youtube.com/watch?v=S9vM4vHyOXU

[calj737]

If you believe it could be oil, then you have only 2 likely sources, valve seals or piston rings. Do you perform a compression test on all 4 cylinders, and if so, what were they? You performed the 3k tune-up, so did you properly adjust the valves? Is #1 out of kilter slightly?

It's difficult to diagnose from the description you give, and from only a 10 second video.

[ekpent]

Was the engine torn down or rebuilt or is there a chance a ring may be stuck from sitting for a long period ?

[Jimsun]

If you believe it could be oil, then you have only 2 likely sources, valve seals or piston rings. Do you perform a compression test on all 4 cylinders, and if so, what were they? You performed the 3k tune-up, so did you properly adjust the valves? Is #1 out of kilter slightly?

It's difficult to diagnose from the description you give, and from only a 10 second video.

ive done the compression test and it came to about 135 +/-5%. Psi on all 4 cylinders.

Are valve seal easier to do than piston rings?

[Old Scrambler]

About the same...............you have to pull the head for either. 

If the bike sat for a few years.................and then you changed the type of oil..............it may smoke for up to 3,000 miles because one or more rings on that piston were glazzed, stuck in the piston-land (grove) or simply worn. That stuck condition may go away, and it may show in the compression test by a very small margin.  If the value seal is leaking...........it will just get worse.......but usually shows worse on start-up and then is mild.  If riding with a friend, ask if they see the smoke when you shift..............that is usually a leaky seal. 

[Jimsun]

Was the engine torn down or rebuilt or is there a chance a ring may be stuck from sitting for a long period ?

About the same...............you have to pull the head for either. 

If the bike sat for a few years.................and then you changed the type of oil..............it may smoke for up to 3,000 miles because one or more rings on that piston were glazzed, stuck in the piston-land (grove) or simply worn. That stuck condition may go away, and it may show in the compression test by a very small margin.  If the value seal is leaking...........it will just get worse.......but usually shows worse on start-up and then is mild.  If riding with a friend, ask if they see the smoke when you shift..............that is usually a leaky seal.

The bike was bought last year. Ive ridden jt around with no smoking issue. I stored it inside my house in the basement over the winter.

When april hits, i road it around for 1 week before removing the full synthetic oil. I believe the smoking started to occur 2 weeks into changing from full synthetic to mineral oil. Will going back to full synthetic help?

Is it possible to pull the top
End, clean/remove/replace the gaskets, replace the piston rings and valve seal and be done? Or will I need to get all 4 walls/surfaces machined. 

Ive done some valve head gasket cover and valve adjustments on cars in terms of engine work.

[calj737]

Just run for a while and see if it clears up. Perhaps you still had oil in the engine/pump when you switched from synthetic. Likely some was still in clutch pack also.

If it really bothers you, run the engine to hot, then promptly drain the oil, change the filter and while oil is draining, operate the clutch lever to aide in moving all of it out.

[Jimsun]

Just run for a while and see if it clears up. Perhaps you still had oil in the engine/pump when you switched from synthetic. Likely some was still in clutch pack also.

If it really bothers you, run the engine to hot, then promptly drain the oil, change the filter and while oil is draining, operate the clutch lever to aide in moving all of it out.

I will grab oil tomorrow

[TwoTired]

Does it still "smoke" after a 20 minute run on the freeway?

Is the "smoke" white, or blue-ish tint, or sooty black?

You can do valve guides (if needed) without removing the head.  I've posted the procedure in the forum before.

Have you checked oil consumption?

In my experience, if it smokes blue-ish worse after full warm up and a long idle period, it's the exhaust valve guides.  Black smoke is over rich and blowing chamber soot out the exhaust.

White smoke is water vapor or unburned and atomized fuel (the later is very rare with all the head pipes getting hot).


Pity you didn't tell us which year and model of the bike.  Is this the 74 CB550?

[Jimsun]

Does it still "smoke" after a 20 minute run on the freeway?

Is the "smoke" white, or blue-ish tint, or sooty black?

You can do valve guides (if needed) without removing the head.  I've posted the procedure in the forum before.

Have you checked oil consumption?

In my experience, if it smokes blue-ish worse after full warm up and a long idle period, it's the exhaust valve guides.  Black smoke is over rich and blowing chamber soot out the exhaust.

White smoke is water vapor or unburned and atomized fuel (the later is very rare with all the head pipes getting hot).


Pity you didn't tell us which year and model of the bike.  Is this the 74 CB550?

Yes its a 74 cb550.

Yes it smokes for the remainder of my rides from start up to finish.

My friends (5-6 of them) says its white but when i look from the mirror its kinda has a blue-ish tint.

On my previous oil change i noticed how my oil level went from top level to low level in 3,000 miles. I thought this was somewhat normal since i was always cruising around 6k 4th gear/powerband (i know  i know but my excuse is that it was single digit degrees up here during that time)

After changing oil, ive put in 100 miles and i havent noticed a change in my oil level yet.

I also want to mention that my air filter chamber bottom outlet is not connected. The outlet at the right side goes to the top part of the engine. The outlet on the left side pointing down is not connected. I noticed how this outlet smokes up too. Should i just cover this outlet?

I have little hope its water as ive ridden for hours and it still smokes.

[TwoTired]

Assuming you still have the internal water separator in the bottom of the filter box, that open bottom drain is bypassing the air filter.  If the plenum air box drain is also un-tubed, then that is also bypassing the air filter.

The filter box drain tube has a pinch slit in the end of it.  Blocks air ingress, lets collected water drip out.
The plenum box drain tube is a reduced diameter ~1/8" opening that had some open cell foam stuffed in it.  This allows gas overflow to drain out, but not let in bugs and dust.

Have you noticed any overheating history for the bike.  Do you know if the valve guide seals were ever replaced?

The additives in some oil blends, including synthetics, have seal softeners (swellers) in them.  A working theory has your old oil, softening/swelling the valve guide seals and better stemming the oil flow past them.  The most recent oil may not have these seal friendly additives or a different less effective kind, allowing the seals to shrink and let more pass down the valve guide.

It's probably a safe bet that if the guide seals are 40 years old, they have likely hardened with heat and age and unknown oil blend exposure.  If resuming your previous selection of oil doesn't help after 100 miles or so, then probably time to renew the valve guide seals.

Consider if maybe the seals were nicely swollen last year, a winter storage period would have allowed the seal renewing chemicals to drain off and the seals would further "dry out".

Just a theory.

You could also pop the cylinder cover, remove a valve spring and see if the guide seals can still do their job.  Your call.  Don't let anyone talk you into a "ring job" until you first eliminate the guide seals as the possible issue.

And if you do take off the cylinder cover, be wary about the shop manual warnings about stem/adjuster interference upon re-installation.  Or suffer from replacing bent valves (head removal/replacement).

[Jimsun]

Assuming you still have the internal water separator in the bottom of the filter box, that open bottom drain is bypassing the air filter.  If the plenum air box drain is also un-tubed, then that is also bypassing the air filter.

The filter box drain tube has a pinch slit in the end of it.  Blocks air ingress, lets collected water drip out.
The plenum box drain tube is a reduced diameter ~1/8" opening that had some open cell foam stuffed in it.  This allows gas overflow to drain out, but not let in bugs and dust.

What's the next step since I do not have that hose? Can i just put a clothe in it's place? It's compact enough that it won't let air in and it'll also drain any liquid in the plenum box

Have you noticed any overheating history for the bike.  Do you know if the valve guide seals were ever replaced?

No I do not notice any over heating. It feels similar to another cb550 that my friend owns. I think the seals are still original as I was never told by the second owner that any engine work was ever done to the bike.

The additives in some oil blends, including synthetics, have seal softeners (swellers) in them.  A working theory has your old oil, softening/swelling the valve guide seals and better stemming the oil flow past them.  The most recent oil may not have these seal friendly additives or a different less effective kind, allowing the seals to shrink and let more pass down the valve guide.

It's probably a safe bet that if the guide seals are 40 years old, they have likely hardened with heat and age and unknown oil blend exposure.  If resuming your previous selection of oil doesn't help after 100 miles or so, then probably time to renew the valve guide seals.

I suppose its due for a valve guide seal. However, could a bad vavle guide seal give the symtom i'm experiencing?


Consider if maybe the seals were nicely swollen last year, a winter storage period would have allowed the seal renewing chemicals to drain off and the seals would further "dry out".

Just a theory.

You could also pop the cylinder cover, remove a valve spring and see if the guide seals can still do their job.  Your call.  Don't let anyone talk you into a "ring job" until you first eliminate the guide seals as the possible issue.

How do i know if the seals are still doing their job? what's the usual give away that they are bad. I suppose i'm better off replacing all the seals instead of replacing one.

Also, how much more difficult is it to go all the way down to do the ring job?

And if you do take off the cylinder cover, be wary about the shop manual warnings about stem/adjuster interference upon re-installation.  Or suffer from replacing bent valves (head removal/replacement).

[TwoTired]

What's the next step since I do not have that hose?

Get the proper hoses, or make something that performs the same function.

Can i just put a clothe in it's place?

I can't imagine that will function as well as the proper parts.  Probably should start by understanding how the system is supposed to work.

It's compact enough that it won't let air in and it'll also drain any liquid in the plenum box

If you say so...  It's your bike.

I suppose its due for a valve guide seal. However, could a bad vavle guide seal give the symtom i'm experiencing?

Oil smoke out the exhaust?  yes.

How do i know if the seals are still doing their job? what's the usual give away that they are bad. I suppose i'm better off replacing all the seals instead of replacing one.

Also, how much more difficult is it to go all the way down to do the ring job?

Go ahead and rebuild the whole engine if you want to.  It's not difficult at all for a skilled person with the proper tools.  How much do you trust your expertise and attention to detail?

Seems contradictory, you won't get the proper hoses, but you want to do a complete ring job without any proof that it is necessary. 

[Jimsun]

What's the next step since I do not have that hose?

Get the proper hoses, or make something that performs the same function.

Can i just put a clothe in it's place?

I can't imagine that will function as well as the proper parts.  Probably should start by understanding how the system is supposed to work.

It's compact enough that it won't let air in and it'll also drain any liquid in the plenum box

If you say so...  It's your bike.

I suppose its due for a valve guide seal. However, could a bad vavle guide seal give the symtom i'm experiencing?

Oil smoke out the exhaust?  yes.

How do i know if the seals are still doing their job? what's the usual give away that they are bad. I suppose i'm better off replacing all the seals instead of replacing one.

Also, how much more difficult is it to go all the way down to do the ring job?

Go ahead and rebuild the whole engine if you want to.  It's not difficult at all for a skilled person with the proper tools.  How much do you trust your expertise and attention to detail?

Seems contradictory, I won't get the proper hoses, but you want to do a complete ring job without any proof that it is necessary. 

Okay. Valve guide seal it is 

[TwoTired]

Okay. Valve guide seal it is 

Best to do all 8 of them if they've hardened up.

[Jimsun]

Okay. Valve guide seal it is 

Best to do all 8 of them if they've hardened up.

Okay. I can confirm 100% that theres anoil leak in cyl 1 exhaust because i could smell the sweet oil scent from the motul full synthetic oil.

Will i need to hone the surface of the top end?

[calj737]

You don't hone the top end, you hone the cylinder bores. If you're removing the head to replace valve seals and guides, best to have a qualified and competent machine shop familiar with these engines perform that service for you. Without specific knowledge and instruments, you can easily do more harm than good.

[Jimsun]

You don't hone the top end, you hone the cylinder bores. If you're removing the head to replace valve seals and guides, best to have a qualified and competent machine shop familiar with these engines perform that service for you. Without specific knowledge and instruments, you can easily do more harm than good.

Hmm I see. Im sure a lot of first time sohc owners should be bringing their bike to a shop to get it done; however, with the right tools and a great community, we can achieve the impossible right? I think I have the entry level experience to tackle this project. I've worked on cars from brakes, brake line replacement, clutch/brake master/slave cylinder, interior mods, electricals, sensor by pass, and minor engine (valve adjustment). It can't be that hard if other first time sohc owners have succeeded. I'd like to be 100% sure on things that's why I love asking questions - measure 5x cut once.

[calj737]

"A man's got to know his limitations" - Harry Callahan
"A lawyer who represents himself has a fool for a client" - Oliver Wendell Holmes

[TwoTired]

Okay. Valve guide seal it is 

Best to do all 8 of them if they've hardened up.

Okay. I can confirm 100% that theres anoil leak in cyl 1 exhaust because i could smell the sweet oil scent from the motul full synthetic oil.

Will i need to hone the surface of the top end?

Way too soon to determine that.

You can commit to big rebuild costs up front and just take it all apart, then replace everything you find not to your liking.  Or, you can get a pretty good idea what needs to be done before taking the motor apart.
Before you tear up the motor, do a leak down test on the cylinders.  This will tell you if you have a compression leak on the rings or valve, as you will hear the air escaping into the crankcase if there is a ring leak. Or into the intake or exhaust ports if you have valve leaks,  If the leak down says no chamber leaks, then it is on to the valve guide seals and do a "wobble" test on the valve stems while the head is still on the motor.  If the stems wobble in the guide, the guides need replacing and the head comes off for that for the guide replacement and a valve job at the machine shop.  If just the seals are hard and not sealing stems to the valve guide, these are examined after you have removed the valve springs (each in turn), simply replace the seals and reassemble.  Ride on.

I'm pretty sure you are itching to take it all apart, and nothing is going to dissuade you from that.  Get ready for $300 to $400 (or more) cash outlay.  Or, buy another used engine and swap it out, for the one that's out of your favor.

[Jimsun]

Any fool can know. The point is to understand - Albert Einstein

When you know better you do better - Maya Angelou

[Jimsun]

Question,

In this exploded diagram, am I looking to replace #36? Should I also replace #1 & #2 or they are reuseable as long as there's no wear or burr.

As for required gaskets, it's #17 and maybe #9 right?
#

[TwoTired]

The valve stem seals are 12209-333-005 (which show on another diagram).

1&2 are the guides, which are pressed into the head, old ones are pressed out.  Do the wobble test, before changing these, and you need to ream new ones to closely fit your valves.  Don't replace unless they are proven worn or damaged.  Which you can find out before head removal.

9 is the head gasket.  Only needed if the head is removed.  And then you need 37, 4, and 39, too.
Yes, 17
38 X 12
also 41 Rubber, sealing 91318-300-013  X 6

There are other orings, too.  42, 40, 12,

[calj737]

Any fool can know. The point is to understand - Albert Einstein

When you know better you do better - Maya Angelou

I would strongly encourage you to read with great determination, what TwoTired wrote. First, understand what is wrong. Then, learn what systems and components perform which function, their inter-dependencies, then isolate the part/parts that are out of spec.

Then decide a course of action. Your last post indicates you've decided what you're going to replace because you suspect it's simply like changing spark plugs: it is NOT. Valve train components have little tolerance for error. Lift, runout, diameter, seating depth, seat angle, etc are highly tolerances machined dimensions. If you do not own machinist grade instruments, then go buy them and prepare to spend a great deal of time learning, making mistakes, and re-doing what you did wrong. No one gets it right the first few times.

Or, remove the head carefully and by-the-book, and take the head to machine shop, and have them perform the work. Take delight in diagnosing the actual problem, and removal and installation of the repaired head. But leave the machinist work to a machinist. Unless you're Mike Rieck or Bill Benton or any other of the extremely experienced engine builders, this is not an effort to be undertaken with glib or wild abandon. Unless you're happy to remove the engine afterwards.

Any way you choose, best of luck-

[TwoTired]

I think I have the entry level experience to tackle this project. I've worked on cars from brakes, brake line replacement, clutch/brake master/slave cylinder, interior mods, electricals, sensor by pass, and minor engine (valve adjustment). It can't be that hard ...

Did all the other mechanical work you did, go smoothly with no mistakes or errors?
Generally when you practice something new, there's an oops or two involved.  Less so when supervised by an experienced monitor.
But, if are willing to pay for your mistakes, you can certainly learn a lot from them?  And, you gain confidence with each success. 

"Experience is a good school. But the fees are high." - Heinrich Heine

"Good judgment comes from experience, and experience comes from bad judgment." - Rita Mae Brown

"Experience enables you to recognize a mistake when you make it again." - Franklin P. Jones

"Do you know the difference between education and experience? Education is when you read the fine print; experience is what you get when you don't." - Pete Seeger

"If we could sell our experiences for what they cost us, we'd all be millionaires." - Pauline Phillips

"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so." - Douglas Adams