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

[Jimsun]

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

All work were done by me with the help of a shop manual and a lot of research/youtube videos. I believe cars are easier in a sense that most of the work is straight up dummy proof(?) assuming you have the right tools and the logical knowledge on how things should work.

The reason im asking for assistance is so i can gain more knowledge before tackling the job. This way ill be more prepared if necessary. I havent done any work on engines but i assume with the right help from the sohc community it would make it easier to do the job.

[calj737]

Don't misunderstand the cautions. They're not meant to dissuade your willingness only to advise you that it's not terribly easy to step someone with little engine building experience through the process successfully over the internet. YouTube or not, there's SO many nuances, techniques, measurements etc to take, that it would be quite a labor to teach over the internet (I am not declaring that I am qualified in my own right, by the way). But I have put together a few V8s when younger, and I know that this is best left to pros. Particularly head work.

Bit if you are willing and determined, then grab numerous manuals, assemble a shopping list of machinist tools, and let's get started!

[Jimsun]

Don't misunderstand the cautions. They're not meant to dissuade your willingness only to advise you that it's not terribly easy to step someone with little engine building experience through the process successfully over the internet. YouTube or not, there's SO many nuances, techniques, measurements etc to take, that it would be quite a labor to teach over the internet (I am not declaring that I am qualified in my own right, by the way). But I have put together a few V8s when younger, and I know that this is best left to pros. Particularly head work.

Bit if you are willing and determined, then grab numerous manuals, assemble a shopping list of machinist tools, and let's get started!

Yes you're right. I have changed my approach to removing the top end and bringing things done to a machinist where necessary.

My approach now is the following (correct/comment me where you see fit)

- Grab the vesrah gasket kit and also grab any OEM gasket kit I can get (This way I will prioritize oem and use vesrah where necessary)
- Remove the top end
- Bring the cylinder head to a machine shop to get it have my seals done and clean the gasket surface.
- Remove the cylinder, do a visual to see if there's any really bad scratches. I will compare mine to my friend's spare cylinder and use whichever one is in better condition to bring to a machinist.
- Once I get everything i'll finally paint the fins and put everything back. At this point it should be slapping it all together right?

Is there anything else aside from #1 I should replace in the same time? ie. #26/27/28/29

Also, If i remove the cylinder, that means I'll have to replace the rings and also rehone the walls right? At this point i'm looking to replace only #2 correct?

[TwoTired]

I have changed my approach to removing the top end and bringing things done to a machinist where necessary.

You don't need to remove the cylinder head, to replace the valve guide seals.

[calj737]

My approach now is the following (correct/comment me where you see fit)
- Grab several good factory manuals
- Grab the vesrah gasket kit and also grab any OEM gasket kit I can get (This way I will prioritize oem and use vesrah where necessary)
- Remove the top end
- Bring the cylinder head to a machine shop to have it evaluated for necessary workget it have my seals done and clean the gasket surface.
- Remove the cylinder, do a visual to see if there's any really bad scratches. I will compare mine to my friend's spare cylinder and use whichever one is in better condition to bring to a machinist. Thats how I'd do it: doesn't make it right, but makes probably better than I can do personally
- Once I get everything i'll finally paint the fins and put everything back. At this point it should be slapping it all together right? You'll be closer to that, euphemistically speaking.

Is there anything else aside from #1 I should replace in the same time? ie. #26/27/28/29 I'd rely on the advice on the machine shop after they've inspected your rings, pistons and cylinders.

Also, If i remove the cylinder, that means I'll have to replace the rings and also rehone the walls right? At this point i'm looking to replace only #2 correct? Not technically required, but a very good practice in my opinion. Also, replace the head gasket and base gasket if you do remove the cylinders.

If you can avoid splitting the cases because everything else loos good, you can focus on insuring the valves (#24, 25), guides, seals and springs are in top notch shape. Use this time to fully and properly rebuild your carbs (a very easily DIY chore that also improves your insight and overall running of the bike. Might think about replacing the cam chain (#13)if you go to the lengths of disassembly. Again, not required, but it's fairly inexpensive. You'll want to study up on the process to remove and re-install accurately (degree ing the cam).

[Jimsun]

My approach now is the following (correct/comment me where you see fit)
- Grab several good factory manuals
- Grab the vesrah gasket kit and also grab any OEM gasket kit I can get (This way I will prioritize oem and use vesrah where necessary)
- Remove the top end
- Bring the cylinder head to a machine shop to have it evaluated for necessary workget it have my seals done and clean the gasket surface.
- Remove the cylinder, do a visual to see if there's any really bad scratches. I will compare mine to my friend's spare cylinder and use whichever one is in better condition to bring to a machinist. Thats how I'd do it: doesn't make it right, but makes probably better than I can do personally
- Once I get everything i'll finally paint the fins and put everything back. At this point it should be slapping it all together right? You'll be closer to that, euphemistically speaking.

Is there anything else aside from #1 I should replace in the same time? ie. #26/27/28/29 I'd rely on the advice on the machine shop after they've inspected your rings, pistons and cylinders.

Also, If i remove the cylinder, that means I'll have to replace the rings and also rehone the walls right? At this point i'm looking to replace only #2 correct? Not technically required, but a very good practice in my opinion. Also, replace the head gasket and base gasket if you do remove the cylinders.

If you can avoid splitting the cases because everything else loos good, you can focus on insuring the valves (#24, 25), guides, seals and springs are in top notch shape. Use this time to fully and properly rebuild your carbs (a very easily DIY chore that also improves your insight and overall running of the bike. Might think about replacing the cam chain (#13)if you go to the lengths of disassembly. Again, not required, but it's fairly inexpensive. You'll want to study up on the process to remove and re-install accurately (degree ing the cam).

So I have purchased the vesrah ''full'' top end gasket kit.

cyl head
#1 12329-323-000 - Breather Cover Gasket - x1
#17 12391-323-000 - Cylinder Head Cover Gasket - x1
#38 91302-001-020 - O-Ring 30.8mm - x12
#40 91303-035-000 - O-Ring 11 x 2.5mm - x3
#42 91319-323-000 - O-Ring 6 x 3mm - x4
#36 91301-200-000 - O-Ring 10 x 1.6mm - x8
#37 91301-323-000 - O-Ring 5 x 2.4mm - x2
#39 91304-286-000 - O-Ring 61.8 x 2mm - x4
#9 12251-374-005 - Cylinder Head Gasket - x1
#4 12191-374-000 - Cylinder Base Gasket - x1
18291-390-000 - Exhaust Pipe Gasket - x4

crank/cam pic
#1 12209-333-005 - Valve Stem Seal - x8
#37 - 91305-323-000 - O-Ring 5.8 x 1.9mm - x1

The following are the things that I need that is missing are...

cyl head
#41 91318-300-013 - Rubber sealing  - x6

Then replace
cyl head
#1 - 12023-465-405 - 4
#2 - 12023-324-405 - 4


Is there anything thing else i'm missing?



if the guides are no longer good.

[Duanob]

My approach now is the following (correct/comment me where you see fit)
- Grab several good factory manuals
- Grab the vesrah gasket kit and also grab any OEM gasket kit I can get (This way I will prioritize oem and use vesrah where necessary)
- Remove the top end
- Bring the cylinder head to a machine shop to have it evaluated for necessary workget it have my seals done and clean the gasket surface.
- Remove the cylinder, do a visual to see if there's any really bad scratches. I will compare mine to my friend's spare cylinder and use whichever one is in better condition to bring to a machinist. Thats how I'd do it: doesn't make it right, but makes probably better than I can do personally
- Once I get everything i'll finally paint the fins and put everything back. At this point it should be slapping it all together right? You'll be closer to that, euphemistically speaking.

Is there anything else aside from #1 I should replace in the same time? ie. #26/27/28/29 I'd rely on the advice on the machine shop after they've inspected your rings, pistons and cylinders.

Also, If i remove the cylinder, that means I'll have to replace the rings and also rehone the walls right? At this point i'm looking to replace only #2 correct? Not technically required, but a very good practice in my opinion. Also, replace the head gasket and base gasket if you do remove the cylinders.

If you can avoid splitting the cases because everything else loos good, you can focus on insuring the valves (#24, 25), guides, seals and springs are in top notch shape. Use this time to fully and properly rebuild your carbs (a very easily DIY chore that also improves your insight and overall running of the bike. Might think about replacing the cam chain (#13)if you go to the lengths of disassembly. Again, not required, but it's fairly inexpensive. You'll want to study up on the process to remove and re-install accurately (degree ing the cam).

So I have purchased the vesrah ''full'' top end gasket kit.

cyl head
#1 12329-323-000 - Breather Cover Gasket - x1
#17 12391-323-000 - Cylinder Head Cover Gasket - x1
#38 91302-001-020 - O-Ring 30.8mm - x12
#40 91303-035-000 - O-Ring 11 x 2.5mm - x3
#42 91319-323-000 - O-Ring 6 x 3mm - x4
#36 91301-200-000 - O-Ring 10 x 1.6mm - x8
#37 91301-323-000 - O-Ring 5 x 2.4mm - x2
#39 91304-286-000 - O-Ring 61.8 x 2mm - x4
#9 12251-374-005 - Cylinder Head Gasket - x1
#4 12191-374-000 - Cylinder Base Gasket - x1
18291-390-000 - Exhaust Pipe Gasket - x4

crank/cam pic
#1 12209-333-005 - Valve Stem Seal - x8
#37 - 91305-323-000 - O-Ring 5.8 x 1.9mm - x1

The following are the things that I need that is missing are...

cyl head
#41 91318-300-013 - Rubber sealing  - x6

Then replace
cyl head
#1 - 12023-465-405 - 4
#2 - 12023-324-405 - 4


Is there anything thing else i'm missing?



if the guides are no longer good.

That's a good start. You never know when you will need this or that gasket later on. The only OEM gasket I would buy is the head gasket if you decide to go down that far. But when you pull the valve seals check for bent valves and valve play in the guides. If it's bad you will end up taking the head off.

[RJ CB450]

I see lots of quotes, lots of complex advice for checking, leakdowns etc.

Will sum up.  Cannot leakdown for stem seals.  Can leakdown for bad valves, but not for the seals.  Cause if your valve is seated, then no air in there.  And any air past the valve is out the exhaust or back through the carbs.

Want to check it easily?  Simply pull off the exhaust.  Look at valve.  Pull off carbs (not quite so easy but...)  Look at the valve.  Or you can use a bore scope and crank engine to open valve.

You are looking for coking on the valves.  They get extremely hot, and after you shut down, oil seepage will bake onto em.  I have torn down enough bad seals, and can tell every time.  Checking when cold, sometimes can even see the oil wet on it.  On OHC engines, often this oil leaking can be seen down the plug hole, will see some oil on top of the piston.  I have a vr6 engine in my garage with this issue, too bad I don't have a pic...

Other signs of possible valve stem seals.  The fact it smokes when you are in rev up.  Vacuum will suck oil past intake seal.  Does it poof bad when you first start it up after sitting, like a small cough of smoke.  Another sign of valve stem seals.

Now, the 550 and 650 setup appear to be almost same thing.  I know my 650, and no hands on or even read up on related or precursory models.  I do know however that for my 650, you can change the valve stem seals without needing to pull the head.  Just need the right tools, and patience.  Proper spring retainers and valve holder, can pop it off and put new one on. 

With leaky seal, I still recommend taking head into a professional rebuilder, get it properly de-carboned and cleaned.  It isn't too expensive for a top quality shop to do.  I did that for my 650 head, worth every penny and took me about an hour to get the head off, and a saturday putting the head on, and tuning the freshly rebuilt carbs.

As for the cylinders, I am going to talk from my experience.  I have never had bad cylinder walls from a proper maintained bike.  Always just needed to be re-honed for the new rings to sit.  Pistons on the other hand, made of garbage it seems so be prepared not for machining, but pistons and re-balance.  If you want to compare, back to my 650:

It was a sitting engine, about eight years at 25K km.  While head was out, I gave a close examination.  No scoring, but was some rust just starting to form.  To keep my budget, I turned the bike on a downward 45 degree lean, and just cleaned the piston heads and cylinder walls by hand.  2000km this year, no burning oil, no issues at all.