Topic: How much work will this be?

[Tretnine]

My 1978 cb550k smokes a lot - an unhealthy  habit. Quite a bit comes off of the blow by and intermittently from pretty much every exhaust pipe. It gets worse as the engine heats up. I know two tired is convinced white smoke is always water vapor, but I'm sure it's not. It hangs in the air and smells. My best guess for the moment, since the bike only has 11k miles, is old, hardened valve seals.

How much work am I in for? I'm assuming I have to pull the whole engine out of the frame just to get at the valves. I don't have valve pulling tools yet, but I'm not daunted by the work and I will buy appropriate tools. (Or build one out of a C clamp and PVC - as seen on the internet)

Is this an afternoon job or a three day weekend sort of affair?

[HondaMan]

It's not too tough on a 550. The head comes off in the frame.

Go to Sears and buy their C-frame valve spring compressor: it will likely be on sale for the Spring soon. It's ideal for removing the valve springs. Get a top-end gasket kit: these contain the head gasket, cam cover gasket, and valve seals, among other bits and pieces you'll want to replace.

When you go to separate the head from the cylinders, consciously try to avoid rocking the cylinders so you don't break the seal at the bottom where they join the engine cases. If this seal is not broken, you can just reinstall the head later. If it does get loose, it will probably weep oil later on, so if this happens you'll want to pull off the cylinders and install the new base gasket. This part is more trouble, as you will be having to reinstall the rings and pistons, which is a bit trickier if you have no experience at it.

If you do it over a 3-day weekend, consider chucking each valve into a drill motor to clean and polish them: they will be cruddy, especially hard crud. Don't touch the shiny sealing ring with your scrapers and emery paper where it seals against the seat, but spin-scrape the crud off and consider polishing the intake valves for a little performance improvement. This will take an hour or so.

Do your valves one at a time so they don't get mixed up: you want to put them back in the hole where they came from.

That's about it! 

[Tretnine]

Very helpful hondaman.  I appreciate your insight and will put it to good use. (Try my best, anyway)

[moham]

Go to Sears and buy their C-frame valve spring compressor: it will likely be on sale for the Spring soon. It's ideal for removing the valve springs.

I might have been doing something wrong, but the Craftsman valve spring tool I used just didn't fit the 550 head right, like hardly any clearance to get the tool over the springs. I had much better luck with the tool sold on sportingforless (although I don't see it listed on their site anymore??)...

I could be wrong, though. I am a bit simple.

[chickenman_26]

My 1978 cb550k smokes a lot - an unhealthy  habit. Quite a bit comes off of the blow by and intermittently from pretty much every exhaust pipe. It gets worse as the engine heats up.

This is not the result of bad valve stem seals. My hunch is that you have broken, stuck, or worn rings. A compression test, or even better, a leak down test will give you a pretty good picture of where the problem is before you tear down the engine's top end.

Is this an afternoon job or a three day weekend sort of affair?

If you have all the required parts and tools and know what you're doing, and provided the cylinders are usable with only a light hone to break the glaze, you're looking at a full day's work. Missing any one of the above items, and there's no telling how long it'll take you.

Stu

[Tretnine]

Stu,  compression at last check was 90 80 90 90. What's the leak down test? I'd rather fix the right thing if you can steer me in the right direction.

[Nikkisixx]

Leakdown test:
1. loosen valve adjustment to close valves which makes cylinder airtight
2. pump air into the cylinder through the spark plug holes
3. measure pressure with gauge over time

If the cylinder "leaks down" you can isolate the valves or rings by where the air goes, and determine the condition by how fast the air leaks out.

You need an air compressor and a leakdown gauge to do this.  An alternative is to put a little oil into the cylinders when the engine is cool and test to see if the compression improves.  If it does, suspect the rings.

[wdhewson]

For valve stem seals, what about his procedure?

Stuff a rope in the cylinder, leaving one end out.  Go to compression.  The compressed rope will prevent the valves dropping.  If the rockers are off, compress the spring and get the collets with a strong magnet.  Pull off the old seal, push on the new.  Repeat 7 more times.  Rockers back in and adjusted.  I've done this on some bikes, but never a SOHC4.  Maybe it can be done, maybe not?

Feedback?

[Tretnine]

Leakdown test:
1. loosen valve adjustment to close valves which makes cylinder airtight
2. pump air into the cylinder through the spark plug holes
3. measure pressure with gauge over time

If the cylinder "leaks down" you can isolate the valves or rings by where the air goes, and determine the condition by how fast the air leaks out.

You need an air compressor and a leakdown gauge to do this.  An alternative is to put a little oil into the cylinders when the engine is cool and test to see if the compression improves.  If it does, suspect the rings.

I don't have a garage so I don't have half of what I'd need to do that test. I can put oil in the cylinders to see if my compression goes up. I tried this in one of my cylinders without any luck, but I'll try the rest of them the next time I've got some free time. fri/this weekend if it doesn't rain.

[chickenman_26]

Stu,  compression at last check was 90 80 90 90. What's the leak down test? I'd rather fix the right thing if you can steer me in the right direction.

Tretnine,
It doesn't sound like you have a way to use a leakdown tester. And frankly, I don't think you need it.
Check your valve clearances first and adjust if necessary, then redo the compression test with the throttle held wide open, and keep cranking till the gauge needle stops rising. If your battery is weak, use the kick starter. If you get the same results, those compression numbers you've posted tell the story. Your compression is relatively even, but way too low. Numbers that low on all cylinders point to the piston rings. Yes, you could put some oil in each cylinder to see if the ring seal improves. But it's highly unlikely you have problems with valves or head gasket in all 4 cylinders, and I suspect there's already plenty of oil in them. So I stand by my original diagnosis - broken, stuck, or badly worn piston rings are allowing oil into the combustion chambers and blowby gases into the crankcase. I'm afraid you're looking at a complete top end teardown, inspection, and repair. It can all be done in the frame, but it's definitely not a weekend project.

Stu

[eurban]

I've said it before in another post by the OP.  It is extremely unlikely that his compression numbers are accurate. First off the offending engine runs pretty well and pulls strongly according to the OP.  Also, engines just don't wear out evenly.  Gauges can easily give significantly lower readings than Honda book values due to the added volume of the testing apparatus  and the relatively small volume of our motorcycles combustion chamber. Proper test procedure is critical as well.  The one cylinder that deviates ("80") is greater than a 10% deviation and the test likely indicates an issue with that cylinder.  Tretnine, I know that you are convinced that your compression readings are accurate and that seemingly you are convinced that your engine has significant issues. Why not go ahead and pull apart the head and see if your need to delve deeper into the cylinders?  Its not a particularly bad job on the 500/550s and it sure seems like the path that you are leading yourself to

[Tretnine]

The motor does pull strongly, which is at odds with my compression numbers. I'm actually only having small problems at idle, which is a bit uneven and clacky (Aside from the smoking) Stu, I think that my first step is going to be to test my compression gauge on another motor, since the hose may have cracked or there may be other problem. I've trusted this gauge because I've used it on many other bikes (4 or 5 CBs + a couple of cars.) With trust-able results. After that, I will probably continue by replacing all the top end gaskets, including valve seals. But, I think I will order a full engine gasket set - that way if the valve seals are not the culprit, I will have a head gasket - and anything else I'll need further down in the motor.

Where is the best place to get a top end/ full engine gasket kit, and is there a good source for hardware. Lots of my nuts and bolts aren't very pretty and while this isn't a show bike, I'd like to replace things that I can, since I'll be doing a fair amount of engine work, it seems.

Brady

[bryanj]

Was this bike unused for some time?

550 rings tend to be Honda only

Valves are same as 500

[eurban]

Idle racket is a given on these motors (sounds like a can of marbles rolling around) but can be improved by anything that smooths out motor's operation.  This would include things like synchronizing the carbs and of course fixing a mechanical problem with a cylinder(s)  The primary chains will slap and the clutch plates will rattle to some degree no matter what you do.  Typically the pchain/clutch rattle is not present when the bike is idling with the clutch pulled in.  Significant noises that are continuously present would indicate cam chain looseness/wear or other more serious issues. . . .A certain amount of visible blow by is inevitable in these motors as well.  . . . Not to beat a dead horse but in all honesty there is no way in hell your motor would run well with actual compression readings as low as you claim.  Forget the absolute values and consider the deviation as the biggest concern.  Make sure however that the low cylinder received the same test treatment as the others . . . .I asked you before the history of your bike.  Has it sat idle for a long period of time? Engines that have sat for a good while will often improve their compression evenness after a good bit of use. Have you ridden it enough to know of other issues it might have?  Does it shift through all the gears and hold gear properly? Basically are there other things that should be done during your engine overhaul.

[wdhewson]

Hi:

In my early work with engines I had a selection of expensive compression testers, but they haven't seen daylight for 20 years. 

Compression readings are a very poor engine diagnostic, to the point of near worthlessness.  The reason being that the gas dynamics in a running engine are completely different than in a cranked or kicked engine.  Compression readings are basically a "yes" or "no" answer, not much more useful than the feel of your foot on the kick starter, providing your foot can tell the difference between compression and opening a valve.

[754]

When you say pulls strong, is that seat of the pants or actual fact, being run side by side with another bike?

 My 836 still ran pretty strong with worn rings, had lots of blowby, if you got stuck thru 2 lights in traffic it would smoke so much it was easier to turn it off, then restart..

[Tretnine]

Eurban, yeah, it sat for a while, but I don't know how long. I bought it from a guy who was trying to make a... he was going for... something. He failed miserably and it sat for a while. Anything could be wrong, because he couldn't even get the points cleaned and all the gaskets were leaking on the top end since he didn't torque things correctly. I cleaned the points and it fired right up.

It starts extremely easily, usually one kick and it feels just like my other 550, though I haven't done an out and out drag race with the two motors. If anything, I'd say this bike handles better than my other bike, which is an abused motor of about 22k.

So 754, my 'pulls strong' statement is subjective. I will have to go through and test compression again since I've put maybe 100 miles or more on it since that last test, and that was my first use of the bike. Before that it was sitting idle.

[diskman]

When you say pulls strong, is that seat of the pants or actual fact, being run side by side with another bike?

 My 836 still ran pretty strong with worn rings, had lots of blowby, if you got stuck thru 2 lights in traffic it would smoke so much it was easier to turn it off, then restart..

HA!  Someone else does this too  .  My '80 CB650 is pretty harsh (smoking badly) at stoplights so I usually kill the engine then restart.  I need to run a compression test also.  sigh.  I do get some strange looks when I am restarting every block or so.  Meh.  Beats the smoke show.

[TwoTired]

My 78 550 also smokes intermittently.  I believe it is the valve guide seals. Most definitely a blue-ish tint to the smoke, hangs in the air, stinks. The deposits in the exhaust have an oily feel.  I think the 77-78 Ks run hotter than previous models (thanks EPA) and harden the guide seals to where they can't conform to the valve stem and do the seal thing.
Compression is fine, good power, and the engine runs too good to yank the head off, there's no oil weep at the head join either.  Plan is to use compressed air or the rope technique to hold the valves in place while the valve spring is removed and the guide seals replaced.

Been too lazy and distracted by other things to do the deed...yet.

[754]

Correct if I am wrong but if you back  right off the throttle on a long hill, for a mile or so, then open it up and it smokes.. it is guides or stem seals.

 Yeah, it sucks tearing down a motor that still runs  so good, but burns oil..

[Lars]

How many miles on your bike?

Sometimes, when the valve stem and seals get warm when running it seals better and less smoke. But if they are hard or broken oil will seep along the valve stems and into the combustion chamber and you will have smoke all the time.

Replacing the seals will take you some time. When you finally have the cam and cylinder head off, you only have a short way to pull the cylinder, too. I will advise you to take the cylinder off, too, and replace lower and upper cylinder gasket and the seals, pluss the o-rings. Mind the two o-rings on each side of the top cylinder for the oil channels. Inspect the cylinders, pistons and rings. Replace the rings, they usually have a mark showing you which side is up.

Use a heat gun and gently a chisel to get the old gaskets off, that is the most boring jobb, defenitely!

When you slide the cylinder back on, have plenty of oil on the lower part of the cylinders. Slide gently - NO FORCE - otherwise your rings easily will be broken. Get a friend to help you holding the cylinder on the other side of the bike and to press the rings and gently slide on. All this done, you will be pleased knowing everything is OK. You would need a cold beer and some heavy distraction from your woman if you only replace the seals and you still have the smoke....

And there is things to mind when you put the cylinder head cover with the rockers back on. The guys on the forum will guide you, just ask...

Good luck with your bike and work!

[TwoTired]

Correct if I am wrong but if you back  right off the throttle on a long hill, for a mile or so, then open it up and it smokes.. it is guides or stem seals.

No, not wrong.  I've used the same metric to diagnose car engine valve seals.  However, that method seems to be more effective when the intake valve seals bad.  A downhill with the intake closed off creates sustained high vacuum in the intake tract which sucks more oil at a faster rate onto the back of the intake valve, which is then burned when power is reapplied and the heat rises.
The exhaust valve stem gets hotter than the intake valve stem, which tends to make the exhaust valve guide seal age/get harder/wear faster.
The pressure in the exhaust tract doesn't usually get to the same extremes as the intake tract pressure differential-wise, so bad exhaust guide seals tend to show oil most any time, and/or randomly. 

Personally I think it is a bigger deal pulling the head off the cylinders, you still have to buy and replace head gaskets, seals, base gaskets, etc., being fastidious scraping the old gaskets without dropping bits into the lower engine cavity, or damaging the gasket surface.  You have to be careful not to plug oil passages, break/strip cylinder studs, damage rings or piston lands when putting the cylinder back on, etc.
Yes, it is all doable, of course. And much easier with experience.  But there is far more risk (and time) going that far into the motor than going down to rocker arm removal (did I mention the cost of the gaskets?).  On the 550, I'm not convinced that the cam has to be removed.  So, I think just removing the cylinder cover, and figuring a way to hold the valves in place with the springs removed, gains you access to the valve guide seals.  Then the only serious worry is putting the cylinder cover back on without bending the valves.
If, for some reason, a valve drops into the cylinder when the spring is off, well then you are looking at that much bigger job.

Jeez, now I am getting enthused to do the seals on mine.  Wish there weren't so many projects ahead of it in the queue.