Topic: 1976 CB550K New Owner of a fixer

[Duanob]

Just a note to say Hi. I just bought the bike in the title but so far it's turning into a bundle of work. I bought it without hearing it run but it turned over. Figuring I would need to rebuild the carbs anyway on a bike that old it didn't concern me. The bike needed a few things replaced to turn her into an OEM bike but as long as the engine was good I wouldn't mind. The good part is the chrome is in great shape, most things are there including a good set of original pipes. The tires are newer and in good shape. The carbs didn't look all that dirty as it only sat for 2 years.

The bad the seat and handle bars are some custom job from the early 80's. There is rust on one fork tube and the seals need replacing (only rust BTW). A dent in the tank and missing missing side cover emblems. The bike has been on it's side more than once so side covers and turn signals need replacing. Someone without skill or knowledge has been monkeying around with things and I find missing bolts and screws everywhere. All cables and a lot of hoses need replacing as well as the carb boots.

Well this past weekend I got the thing started up but the number 3 cylinder smokes like a chimney! They all smoked for a bit but settled down after a few minutes of running. BTW it ran better with the choke on than off. The number 3 (second from the right side?) still smokes and has oil coating the end of the exhaust pipe. Not good! What are my options? Is it just a bad valve, scored cylinder wall, broken ring, bad head gasket? Is there some tests I can do to narrow it down. If it was just a gasket or bad valve I may just have fix it.

Anyway thoughts , experiences?

[flybox1]

what color is #3's smoke?
Find a Clymer, and download the shop manual.
Do your full 3000mi service and completely go over your carbs like 50 times before putting them back on. 
get back to us with how it runs after.

nice find BTW!

[Duanob]

Howdy neighbor and thanks for the reply. Pretty sure it's oil smoke I wiped the end of the exhaust hoping it was raw gas but nope. I'm not sure at the moment if I want to put the effort into this bike or just start over. Like I said when I bought it I thought the motor was in good shape I wouldn't mind putting forth the effort. I think figuring out the smoking cylinder will be my first thing. Can I tell if it's a bad valve from the tappet adjuster hole? I tried to do a compression test but Honda motorcycle uses a weird size hole and not easy to get at the plug in the two middle cylinders. Looking for tools if you know anywhere in the puget sound region to get them?

I looked at a 77 cb550K last night that is awesomely original and super low miles that was a 30 year storage barn find story. The only thing wrong with it is the engine is seized carbs are gummed and a little bit surface rust. For $600 and only 4000 miles it's worth at least for parts. It would be worth rebuilding the engine and driving it. BUT I have to say I am torn. I like the looks of the 74-76 550K way better. In 77 they modernized the bike a bit with different exhaust, lost the fork gators, and lowered the turn signals. Not crazy about the 77 color schemes either. What to do, what to do.

[TwoTired]

You need that compression test.

Or you can try to vacuum sync the carbs.

[Duanob]

That's what I thought. Any ideas on how to fit a normal comp tester to a Honda spark plug hole? Are the plug threads metric? If not I can find some brass fittings and rig something up. First I have to get the plugs out! I have a pretty full tool set having a Ford, a Honda civic, and a boat but not many tools that fit the Honda bike.

Here is a thought, trying to eliminate the worst case scenario. If I had a scored cylinder wall or broken piston ring, would there be a lot of pressure at the oil fill plug? If I started the bike with the oil fill plug removed I should be able to feel pressure, right? If not then maybe I'm OK as far as the piston casting is concerned. My feeling is if I have to do a total rebuild then I may get rid of this thing and start over. If it's just some top end work then not a big deal.

[TwoTired]

Spark plug threads are 12 mm.
There are adapters available for compression testers.  Have you tried some MC shops?
I've no idea which comp tester you have, though.

Invest in a Honda spark plug tool.  Like comes in the stock tool kit.  I works quite well clearing the obstacles in the plug access tunnel.

At the top of the engine is a crankcase breather tube.  If you have excessive blow by, you can check for pressure there rather than the oil fill plug.

Have you downloaded the Honda Shop manual yet?  Wealth of info about the machine in there.

[Duanob]

I downloaded one of the manuals off this board but it seemed to be missing a couple of pages. I just got may Haynes manual yesterday but it is missing a couple of chapters! No tune-up/maintenance just dis-assembly and re-assembly. It's pretty thin. The timing chain sounds loose and noisy I was hoping to learn how to adjust it but not in the haynes manual.

My comp tester is a basic auto type. Fits 2 size holes just not MC.

Tossing around the idea of parting it out and starting over with a better project. What would the pipes be worth in good shape? Also wheels and fenders worth? All chrome is in great shape. Just curious. Funny. there was a guy selling an engine on ebay with a video to show how it runs. It smoked worse than mine! I wouldn't touch it unless you want to rebuild.

[Duanob]

Sheesh the more I get into this bike the more frustrated I get. I bought a tool kit from my local MC salvage place not for a CB550 but for a Rebel. Most tools are similar especially the spark plug tool, and it was only $15! I took the #3 plug out just to see. It was an NGK #8 heat range. I took out the #4 plug to match and it was an OEM #7 heat range. Not  huge problem but really makes you wonder about everything else on the bike. Nither were really oil soaked but a little on the black color range. It's a good thing this bike looks great in my driveway or else...

I think I need to have a little patience with this thing. Take one step at a time and realize I may not be riding it this year. Step one at this point is to rebuild the front end and leave everything else alone. Baby steps. I got some parts coming from ebay, new gauge bracket with tach attached for the chrome trim (both damaged) and fork gators and seals. I need new grips, OEM bars, brake master seal kit and hose. I'll check the brake pads when I get it apart. The good news is the wheel and fender are in fantastic shape, no rust or dirt. Once the front end of the bike is in origianl looking shape I think my attitude will change. Then move on to the next section, the motor. Either try and see what's wrong with this one or look for a good used on already running. I'll keep my eyes open and ears to this board. Thanks for now. I'll post questions as they come up.