@twotired if I open up my top and find a similar wobble in my valves would you advise I put it out of service until I fix it? also I have heard that some riders will continue to ride on bad valve guides but I am unsure as to what the long term effects on the engine are. Willl it eventually lead to a catastrophic failure?
I more or less put mine out of service when I diagnosed the valve guides. Of course, I have several others to ride, too.
My understanding is that the valves move about in their seats rather than simply closing in the same place they did last closure. Stands to reason that the valve seal will be compromised progressively with further use, losing compression and eventually burning valve and or seat. They will continue to run (and smoke) for a long while. But, I don't know how to quantify a "long while". I just know the run life will be shorter than an engine with good guides and seals. And peak power has to be diminished, as well. If the valves and seat are still good now, then stop using it, to save them. If they are already worn, wearing it more, will still need the same treatment, to correct and just a little too much wear. I can't see anything breaking catastrophically, just because of worn guides. But, the mosquito population may be impacted.
Some of my friends at the shop say if the guides are busted it might be wiser to just sell the bike and pick up another but I am a very hands-on-fix-it-no-matter-what-it-takes-even-though-this-is-my-first-time-opening-up-a-motorcycle. What do you think?
I tend to take responsibility for any issues that come up with the bike, and feel I should fix it. There are certainly others that would rather pass problems along to an unsuspecting or uneducated buyer. I'd rather save the bike for more service. If the new owner junks it because of repair costs, I'd feel bad about it, as other wise it's a very nice bike with more life left in it. They don't make them anymore.
I would love to do all the work myself and I will do proper research before I attempt it but I have grown quite the sentimental bond with this machine. I am willing to pay a professional for some of the more difficult aspects but I swear after watching that video I feel like I can do the entire top end in a day or two...
It does take specialized tools to do the guides properly and restore the valve seats. I do wonder about the valve damage. I'm not sure if the valve faces are hardened, how deep they are hardened and if they can also be resurfaced with original reliability. If not, then probably all the exhaust valve need replacing, too. Not sure you can know that until it's dismantled.
Of note: The 78 was made to be a lean burn engine in stock form. And, it was known that a hotter engine burns fuel more efficiently than a colder one. In cars of the era, they raised the thermostat opening temp. In this bike they just allowed the engine to run hotter to improve emissions. There is also some question about the guide materials. The 77- 78 750 F models were notorious for early valve guide wear out. And, a new guide material was used to help with that early wear out. They also had valve geometry issued due to the larger valves of the F model. Anyway, I speculate that they used a too soft material for the guides in that F model, and just maybe the 77-78 550, too, used the same supplier and material. Along with the increased heat breaking down the oil sooner than early models, the result could easily be early guide wear out for the 550. Of course I only have a test case of just one 78 CB 550K, which is a pretty small sample size. But neither of my 77 F models, or other 550s have issues with valve guides. So, I suppose I'm a bit jaundiced about the 78 550 guides. I should also note that I got the bike with about 20K miles and have no data about oil change frequency or type of oil used.
I seriously doubt that with 24K miles on my 550, that the pistons, cylinders or rings are not yet an issue on mine.
I have a guy in California that can do the 550 head work restoration for a reasonable price. Of course, now I'll have o pay shipping to/from AZ. But, I know he'll do a good job, as he worked for Honda at one time before opening his own shop and has all the tools required. I'm thinking about paying him, so I can do some of the other hundred projects I have to do.
Cheers,
