Author Topic: 1978 CB550K NOOB Needs Help (Read 3620 times)

wildbill903 · « **on:** March 28, 2006, 10:31:04 AM »

Hey all; I'm new here. Just looking for advice. I recently acquired a '78 CB550K, didnt run when i got it. I've been working on it here and there between other things. Long story short, i finally got a battery for it last night, charged 'er up adn threw it in. The starter cranks great, unfortunately, she's not kickin over. At this point i dont know how to proceed. Anyone have any ideas where to check first? Also, I dont know whether to administer the chopper treatment or give it some cafe style. Y'all let me know what you think.

my78k · « **Reply #1 on:** March 28, 2006, 10:45:26 AM »

I think I'd wait til it ran before worrying about what to make it look like

Well, first of all check for spark on all 4 cyl's then check the carb's to ensure you're getting fuel.

More of a history would help too...when did it run last etc.

Would be willing to bet money that you'll need to tear off the carbs and clean out the idle jets atleast...

I'm sure more folks will throw in their 2 cents and most of them know a heck of a lot more than I ...remember the bike really one needs 3 things to run: 1- air 2- fuel and 3-spark...tackle those first and foremost...

Dennis

eldar · « **Reply #2 on:** March 28, 2006, 10:50:25 AM »

check for spark. Make sure fuel is off and pull the plugs out and lay them against the cylinder head and try starting. See if there is any spark. Make sure fuel is getting to the carbs. No fuel = no go.

If you have fuel and spark, then check your timing.

wildbill903 · « **Reply #3 on:** March 28, 2006, 11:58:13 AM »

So far as i have had it, a year, it hasnt run. I was told by the fella that gave it to me that he at one point, about a year before that, had gotten it to turn over. Before that it was stored in a basement for about 5 years. I am guessing that i needs to clean the carbs, i just dont want to throw much more money into it. Thanks again for all your help fellas.

bill440cars · « **Reply #4 on:** March 28, 2006, 12:13:08 PM »

Say, while you've got the plugs out, to check for spark, why not run a compression test
(if you have or have access to a compression gauge) and see what you have to work with in
that area? The other things mentioned should be checked of course. Chances are, you won't
have a problem in the area of compression but, that info could come in handy later. Just a
thought. Later on, Bill

wildbill903 · « **Reply #5 on:** March 31, 2006, 06:44:08 PM »

Eureka;
tonight i got the old beast to run. man did it feel good. here's the thing, it wouldnt stay running. the longest i got it to run for under its own was about 30 seconds, and it idled at about 3000 rpm. anyone know how to regulate that? also, it wouldnt run without the choke, but im just assuming thats because it was so cold.

TwoTired · « **Reply #6 on:** March 31, 2006, 06:51:23 PM »

Quote from: wildbill903 on March 31, 2006, 06:44:08 PM

Eureka;
tonight i got the old beast to run. man did it feel good. here's the thing, it wouldnt stay running. the longest i got it to run for under its own was about 30 seconds, and it idled at about 3000 rpm. anyone know how to regulate that? also, it wouldnt run without the choke, but im just assuming thats because it was so cold.

Classic symptoms of plugged slow jets in the carbs. Did you check the head pipe temps? Colder ones are the carbs that need attending, assuming some of the slow jets are working.

Cheers,

BobbyR · « **Reply #7 on:** March 31, 2006, 07:11:52 PM »

A Word of caution about checking the pipe temps. DO NOT TOUCH THEM. I have heard of people flash touching them and that would be really innaccurate. A simple method is to put a drop of oil on each pipe close to the flange. Observe the oil drops and see how long each one takes to bubble and burn off, if all is well they should burn off at roughly the same rate. Very simple and very safe. If you have a heat sensing laser gun that would be balls on, but how many of us do? You can fill the bowls via the the main fuel line with some Yamaha carb cleaner, Seafoam or similar product and let it sit for awhile. You may loosen some crud up and allow it to run longer. I did that to see if my motor was shot, when I had no oil burning or other weird things, I knew I had a runner and invested a few hours in taking the carbs off and cleaning them.

Noel · « **Reply #8 on:** March 31, 2006, 07:43:55 PM »

This place has a love affair with the Yamaha carb cleaner, and I'm a recent convert. It's good stuff.

I know there's an old thread floating around with someone's secret method of mixing one part Yam carb cleaner with three parts gas, injecting a certain amount down the fuel lines, cranking the kickstarter a few times, and letting it sit. I wondered, for a while, how they came up with that idea. Then I bought a few bottles of the stuff and realized that those were the actual directions.

Personally, I am never going to tear down another set of carbs without first trying that method.

Were it my bike, I'd replace the plugs, make sure my battery is doing what it's supposed to, check the spark, run a few bowls of Yam cleaner through the carbs, check timing and valve clearance, put fresh gas in the thing, and hit the starter. If you check all that and make all of it right, it should run, if badly. If it won't run at all, you've got a heap 'o trouble, methinks.

Killer Canary · « **Reply #9 on:** March 31, 2006, 08:01:37 PM »

A '78 K should have a dash-mount choke with a fast-idle setup. Assuming you were using the choke, this would account for the high idle speed you noted.
Mine was sitting under a tree for five years before I found it; as a matter of routine I flushed the fuel tank and pulled and cleaned the carbs thoroughly; after turning over for a couple of seconds it caught and ran on all four. Your problem probably isn't any more serious than that.

TwoTired · « **Reply #10 on:** March 31, 2006, 08:05:28 PM »

Quote from: BobbyR on March 31, 2006, 07:11:52 PM

A Word of caution about checking the pipe temps. DO NOT TOUCH THEM. I have heard of people flash touching them and that would be really innaccurate. A simple method is to put a drop of oil on each pipe close to the flange. Observe the oil drops and see how long each one takes to bubble and burn off, if all is well they should burn off at roughly the same rate. Very simple and very safe.

You are, of course entittled to your opinion. However, I have been flash touching head pipes for years to determine relative temps. Still have all my fingers and no burns. Inaccurate, perhaps, but a cold pipe is pretty easy to differentiate from a hot one. I don't need to know what the actual temp is, just if it is different from the others. To use this proceedure without injury you must always assume the pipe IS hot. Your skin has a memory that will allow you to feel the heat after you have removed it from the very brief contact you have made with the pipe. You can do the same trick to an open match flame. Pass you finger through it quickly, and you feel how hot it was after your finger is removed from the flame. If you want a warmer finger do it slower. Same procedure with touching the head pipes.

Oiling the pipe to watch it boil also has the risk of turning Chrome pipes blue.

Nice tip with the carb cleaner, though.

Cheers,

bill440cars · « **Reply #11 on:** March 31, 2006, 08:45:35 PM »

TwoTired, flash touching, as I've now heard it called, is the way that my Dad taught me. He said that if you use the back of your fingers, you can pull away quicker and to this very day(so far)
I haven't gotten burnt or blisters. I mean, the main thing you need to know is if that cylinder is firing or not. Later on, Bill

Kelvin8 · « **Reply #12 on:** March 31, 2006, 09:44:57 PM »

If you search "slow speed jets" you'll find the procedure for cleaning them, the issue has been addressed before here. Make sure you clean all your fuel lines and bowls thoroughly. When the jets are clean you'll get a strong stream of cleaner through them, not a dribble.

csendker · « **Reply #13 on:** March 31, 2006, 09:57:05 PM »

Quote

Oiling the pipe to watch it boil also has the risk of turning Chrome pipes blue

You mean there's supposed to be chrome on the pipes?? I thought I was getting a deal because mine came standard with rust. Boiling oil all over my pipes may actually improve them. Actually, I recently used the touch method when I screwed up my points. It was running real crappy, so I checked and found 2/3 cold. Played with those points and got it running OK again. But think about the back of your finger/hand. Natural reflex from heat (and electrical shock) is to close your fist. This, of course, is not a good thing with a hot pipe or live wire.

wildbill903 · « **Reply #14 on:** April 01, 2006, 08:39:43 AM »

Thanks guys, for all the help with this.

I cant tell you how excited i am about this bike. I'm gonna clean out the carbs good this week, and ill keep everyone posted on the outcome.

wildbill903 · « **Reply #15 on:** April 04, 2006, 09:05:10 AM »

no time to really check anything yet, but another question. I noticed the carbs are puking fuel out of the little rubber hoses attached to the bottom of the carb. Can that have anything to do with the slow speed jets? gonna go get me some yamaha carb cleaner later on today. Thanks again fellas - Billy

TwoTired · « **Reply #16 on:** April 04, 2006, 09:30:36 AM »

Yes, the same bits of crud that block the slow jets can also block the float needles from closing, resulting in overflow.

If you have rust scale in your tank/ carbs. Carb cleaner will not disolve these bits.

Cheers,

hobieguy213 · « **Reply #17 on:** April 04, 2006, 10:20:10 AM »

I have a '78 cb550 that sounds like it was in similar shape to yours. You should reallly pull the carbs off. On mine, the float needle in the carb for #1 cylinder was complete sealed up with rust etc. It was flooding out the other carbs as well I think. I think it was from resting on the kick stand on that side for so long. Pulled 'em cleaned changed all the float needles and they worked great. Stopped leaking from the drain too.

I have one side question. There is a nozzle next to the gas input in the carb assembly. Looks the same as the gas nozzle just a little smaller and they are side by side between the #1 and #2 carb. When I got the bike this wasn't hooked up to anything. Should it be? What the hell is it?

dusterdude · « **Reply #18 on:** April 04, 2006, 12:00:51 PM »

do these carbs have stand pipes like the earlier models?

wildbill903 · « **Reply #19 on:** April 04, 2006, 12:15:03 PM »

While I'm at it, anbody have a link to some parts diagrams for the carbs on this bike? Suggestions on where to get the cheapest carb gasket kits? Again, new to this on these carbs-

hobieguy213 · « **Reply #20 on:** April 04, 2006, 01:17:47 PM »

Duster dude could you describe what you mean by stand pipes (I don't have all my technical lingo down yet)?

I got my gaskets from crc2onlinecatalog.com they were cheap.

hobieguy213 · « **Reply #21 on:** April 04, 2006, 01:20:02 PM »

The Clymer manual for these bikes has a keihin carb exploded diagram but the bottom end of it is wrong for the '78 (you can still pretty much figure it out from there though).

bill440cars · « **Reply #22 on:** April 04, 2006, 02:05:41 PM »

Another place to check is crotchrocket.com

TwoTired · « **Reply #23 on:** April 04, 2006, 03:46:13 PM »

Quote from: hobieguy213 on April 04, 2006, 10:20:10 AM

You should reallly pull the carbs off.

That may be necessary, but, I'd drop a float bowl first to verify the need.

Quote from: hobieguy213 on April 04, 2006, 10:20:10 AM

I have one side question. There is a nozzle next to the gas input in the carb assembly. Looks the same as the gas nozzle just a little smaller and they are side by side between the #1 and #2 carb. When I got the bike this wasn't hooked up to anything. Should it be? What the hell is it?

It is a carb bowl vent. Dust and dirt that settles there winds up in the float bowl fuel. There is supposed to be a hose that routes and ends between engine and swing arm. The long tube virtually eliminates a contamination problem.

Quote from: dusterdude on April 04, 2006, 12:00:51 PM

do these carbs have stand pipes like the earlier models?

Yes, they have them. What is different, is the drain screw opens the bowl to the bottom of this tube instead of immediately overboard.

Cheers,

Quote

wildbill903 · « **Reply #24 on:** April 05, 2006, 06:16:56 PM »

Big Announcement! Took the carbs off tonight , cleaned the bowls good, all the sludge is out. I put it all back together, threw them back on the bike, held the butterflies colsed and she purrs like a tiger. only problem, the choke cable isnt workin quite right. anyone have a link to some pictures of how the cable goes onto the linkage so i can get the whol thing buttoned up? again, greatly appreciated. later; bill

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Author Topic: 1978 CB550K NOOB Needs Help (Read 3620 times)

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