‘78 Honda CB550K Four

W0LF6ANG

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Location
Watsonville, California
So i got this motorcycle over the weekend.

Not having much luck finding replacement air box boots. I can only find ones that fit earlier models but not for this year model. Guess different style carbs used.

I know this is mainly a twin forum but im hoping someone has found an alternative.

Also want to check in here before i join the other forum meant for CB Fours.

Thanks you.

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It seems that Honda didn't offer the hoses separately from the airbox at that point. Not sure if the carbs are that different that the earlier hoses wouldn't work, but according to the fiches at CMSNL it would seem that the 550 carbs have been the same since the model started, or at least similar enough that the hoses should interchange. You might have to buy a used airbox complete to get what you need.
 
I know i probably need a new one, but what could have caused this and how to prevent it from happening again?

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Better insulation. That looks either heat or chemical. Electrical tape isn’t great in fending off either.
 
I moved your posts to your existing Other Hondas thread for this bike to keep it all together.
W0LF6ANG said:
I know i probably need a new one, but what could have caused this and how to prevent it from happening again?
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Notice how the melted wires are green? Something was shorted to ground (green is ground on virtually all Honda harnesses) with significant amperage, that's how that happened.
 
Oxidized contacts lead to higher resistance, lead to heat dissipation, lead to burned isolated area’s since the heat can go nowhere. The damage to the connector is severe, and should be replaced. And, as AD says, look for short circuit wires.
 
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ancientdad said:
It seems that Honda didn't offer the hoses separately from the airbox at that point. Not sure if the carbs are that different that the earlier hoses wouldn't work, but according to the fiches at CMSNL it would seem that the 550 carbs have been the same since the model started, or at least similar enough that the hoses should interchange. You might have to buy a used airbox complete to get what you need.
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Just for the record, definitely not the same throughout the models, although I'm not positive about fitment for the connectors to the airbox or the engine. Honda used 5 different model carbs throughout the run (including the 500s): 627B, 649A, 022A, 087A, 069A, with different jettings and settings, and that's just up to 1976. The later (77 and 78) were the most different from the earlier years. Again, not sure about fitment but there you go...
 
another question regarding the wire harness. since the wires on the rectifier look damaged as well , will i need to replace it? or just rewiring it will be enough? also, who sells a good replacement for a reasonable price. thanks again.
 
W0LF6ANG said:
another question regarding the wire harness. since the wires on the rectifier look damaged as well , will i need to replace it? or just rewiring it will be enough? also, who sells a good replacement for a reasonable price. thanks again.
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It's very possible the ground wire got melted into other wires in the harness, so it might simplify things for you to replace the harness. Fortunately we have the source for the best value in wiring harnesses and modern components for your electrical system. The owner of Sparck Moto and Vintage Connections is also a member here (@Sonreir) and he offers great support for his products, which are as high a quality and as reasonably priced as any you'll find.
 
The carbs for 77 and 78 use PD carbs and are entirely different. Because of this the boots are different lengths.

OEM float valves and proper synchronization is very important. Carefully adjusting the timing on these bikes is mandatory or you WILL get hanging idles and other strange running that will make you think it is carbs. I have a rough draft video on setting the timing for these bikes. If interested PM me for a link on that.

Again, timing is VERY important. ONLY use TEC points. DO NOT get Daiichi points. REPEAT - DO NOT USE AFTERMARKET POINTS ON THESE BIKES. DO NOT USE AFTERMARKET FLOAT VALVES ("NEEDLES") ON THE CARBS. IT WILL NEVER RUN RIGHT.

Be sure to adjust the valves (I have a video on this as well, it's done but needs some small revisions on the captions, PM me for that) and recheck compression. If it's under 150 then it's rebuild time. Really? Yes, really.
 
Here's a couple of videos I made that are done in regards to these bikes

Clutch adjustment:

Cam Chain Adjuster - This is important to go over that slotted screw because there's a lot of FUD on SOHC4 forum (please don't go there if you value and cherish this bike):

Another thing is don't believe SOHC4 forums that you these bikes have serious charging issues. I'm personally running a 3 ohm DynaTek (highly recommended you get a 2, 3 or 5 ohm DynaTek and make your own solid core wires) ignition coil with no resistor caps and no resistor plugs. Gapped at 0.040". AND an H4 headlight. No charging issues. If you're getting strange charging issues it's usually the key switch and internal resistance around the reg/rec circuit and the fuse box. Definitely check the fuse box as my main fuse terminals failed in that box years ago before I knew what I know now.

I recently put a set of Michelin Road Classics on this bike, and it made a huge difference. If you have the $$$ in your budge it's highly recommended.

Here is an excel document with list of o-rings, seals, etc. with their part numbers and if there are equivalents from McMaster-Carr then those part numbers are listed: https://docs.google.com/spreadsheets/d/1ZYwWdKcQqxgmHu_1lxAMLqXclFfZhVQCxa3Rh4EFRBg/edit?usp=sharing

Recommend you buy a bag of the o-rings for the intake manifold and valve inspection caps. It's part number 9262K743 from McMaster-Carr. Use grease on re-assembly. When tightening the valve inspection caps go about finger tight then maybe like 1/4 to 1/2 a turn or so. Do not he-man those on or they may be difficult to remove in the future or even crack. If they do crack that part is still available from Honda.

Sorry for back-to-back posts, but I hope this random dump of information is very helpful to you. A lot of bad information on there on these bikes.
 
Without re-litigating the he-said, she-said that always happens (and ignoring the personal beefs that some people have here with some people over there), and simply in defense of the SOHC forums, they are worth signing up to if you have an SOHC4. No forum is immune to occasionally incorrect information -- it happens here too, including in this thread, although this is a twin forum -- but there is plenty of great info over there as well. In other words, don't throw the baby out with the bathwater.

Have a look at the "Beware of forums" in the link -- ironically posted for you to check out on a forum.

Again, not here to re-litigate or choose sides, an not interested in starting an argument, but no forum is perfect and I think you'll find some good info and good people over there. Or at least have a look and make up your own mind.
 
Wrong. Taking advice from there is very bad. If you value your 550 and want it to run correctly you will avoid most information over there. You're much better served reading the FACTORY SERVICE MANUAL (NOTE, UNDERLINED, NOT THE CLYMER!), studying it, and coming back here if you need further advice. We have people here who actually SERVICED these bikes in a PROFESSIONAL ENVIRONMENT when they were new! SOHC4 contains people who claim to have worked them on but have no real qualifications or resume on that. This wouldn't be such an issue if it wasn't for the fact that these bikes do require specific tuning procedures that are now lost on a younger generation of people. The tuning is not difficult, but it is not intuitive if you have never done it before.

Basically: the charging systems are not junk if you are just trying to ride it around without a bunch of crap hooked up to it, the PD carbs are not "difficult" to work on, the slot on the cam chain tensioner IS used for adjusting it - sometimes they do (and more so now than ever) get stuck and need turned a bit to see if they "snap" back if they don't that is a problem, the idle does not require frequent adjustment while riding, the bike is supposed to idle around ~1050 RPM, the voltage regulator CAN be adjusted and may be beneficial if you do a lot of short trips (the adjustment procedure is even in the FSM!), ignition point timing is not difficult and it is reliable but you must do it and check it every so often.

If anyone tells you otherwise on the points I just listed, then do not listen to them. Do not trust any information they give you about these bikes. That sounds very extreme and black/white. But it's really true. A lot of idiots out there. The SOHC4s attract knuckleheads more so than other vintage hondas.
 
You clearly have something personal against someone there, and you've said as much before. Please get over it.

As I said, there is incorrect stuff on every forum, including here. But there is by far much more useful information here, and over there as well.
 
If you think what I am saying is hyperbole or overexaggerations check out this thread someone PM'd me on: http://forums.sohc4.net/index.php/topic,187628.50.html

HondaMan rebuilds an engine and it seizes. Funny. Also, for a guy like Mark who posts in literally almost every thread he's silent on that one. That happens every time he gets called out by the way. It's not just Mark, there's other people with insane post counts who do bad work and give bad advice and when you call them out they pretend to not hear it.

Just trying to prevent others from being SOHC4-pilled. Why continue to defend these guys? These guys post in almost every single thread saying dumb stuff all the time. It's dubious his credentials and somehow being an EE makes it OK? I'm a software engineer. I know a fair amount of things on some select models discussed on this forum, however when I'm wrong and someone corrects me I apologize and make an effort to not make that mistake again. What's their excuse?
 
Maraakate said:
If you think what I am saying is hyperbole or overexaggerations check out this thread someone PM'd me on: http://forums.sohc4.net/index.php/topic,187628.50.html

HondaMan rebuilds an engine and it seizes. Funny. Also, for a guy like Mark who posts in literally almost every thread he's silent on that one. That happens every time he gets called out by the way. It's not just Mark, there's other people with insane post counts who do bad work and give bad advice and when you call them out they pretend to not hear it.

Just trying to prevent others from being SOHC4-pilled. Why continue to defend these guys? These guys post in almost every single thread saying dumb stuff all the time. It's dubious his credentials and somehow being an EE makes it OK? I'm a software engineer. I know a fair amount of things on some select models discussed on this forum, however when I'm wrong and someone corrects me I apologize and make an effort to not make that mistake again. What's their excuse?
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ENOUGH!
 
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