Topic: 1977 CB550K running issues - seeking help

[Can550]

Hi guys
I have had tremendous help on my other projects in the past so here I'm again with some older repeating issues and some new (to me) and seek your help.

I recently acquired a 1977 cb550k and seller rode it behind me to my house. I then took a small round and it ran strong.

Next morning I was unable to pull the choke (stuck) and it did not start. I then cleaned tons of gunk and lubed the choke cable, it fired up right away but ran terrible. Vibration, misfiring, popping and rough idle. Surprised what happened overnight

I then started to investigate and found boot clamps were rather loose, tightened those but not huge difference

I removed carbs, cleaned them well (they looked clean and recently built). One of the mixture screw O ring (tiny thing) looks like it was pinched so it does not seat properly (I'm assuming looking at its shape).

However put the carbs back on and it started with choke, release the choke and it died right away. Didn't accept any acceleration without choke, lot of hesitation and died very quickly. Tried to sync carbs but bars on sync tool stay at bottom and show no movement (my carb tool is fine).

Removed carbs again, looked inside, seemed fine. Now I will put them back on once I have some direction to fix.

Oh by the way it's all stock. Valves and timing adjusted, battery newish and fully charged, fresh gas, fresh oil and filter. Spark plugs are D7EA, caps are 5k ohms. Stock pipes, stock jets 90 air filter newish. Only missing bits are tube from filter box and tube from Air plenum/ box. Would it make any difference ? 

When ran with choke, popped everywhere, pipes, carbs.

Appreciate direction to have it running for remainder riding days

Cheers


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[calj737]

First 2 things that jump out to me is you make no mention of fuel level in the carbs. Use the Clear Tube method to determine that.

Pulling the carbs and giving them a full, and proper cleaning is a bit more involved than spraying carb cleaner in them. There are emulsion tubes, jets, needles, etc that all need detailed cleaning. "Stock 90" jets sounds quite wrong too, depending upon actual carb model. ("Requires choke to idle" is a pretty strong indication that you're very lean)

Plugs should be DR7 when you get the carbs cleaned up.

[Jamus]

Did you remove and clean the pilot jets?  They are pressed in, and can be removed with vise grips and a small piece of leather to protect the brass jet.  Soak in acetone while you clean the pilot circuit passages.  Clean the pilot jets with a guitar strings.  BTW, the manual supplement says the factory pilot jets are#38, but most people find #42 in theirs.

[Can550]

Yes
I removed and cleaned #42 jets
Sprayed carb cleaner through passages. Cleaned jets with guitar string and thine copper wire strand.

Do I need to fish wire strand through passages ?


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[Can550]

Put the carbs back after thorough cleaning of each part. Luckily overflow leak from carb 4 is no longer there.

Everything else is same. Starts right up with choke.

Doesn't take any throttle.

RPMs go up itself then dies.

Mixture screw tried at 1, 1.5, 2 turns out.

Exhaust 3,4 blowing hot air, 2 warm and 1 cold.

Frustrating to see that Carbtune bars don't even move except with choke.

Help pls.


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[jgger]

I'm not a carb expert, but I did stay at a Holiday Inn once...... If it only runs with the choke on that would make me think there is a huge air leak somewhere. Are the carbs seated good with no folds in the boots? Are the boots intact, no cracks or tears?

[calj737]

#1 being "cold" is still an indication no fuel or spark. I'll bet on fuel. Still no mention of Clear Tube measurements. Don't bother sunching them with a vacuum synch until the bike will idle normally. Surging RPMs is indication of a vacuum leak (either boots or manifold O-rings.

[Can550]

Thanks everyone
It's boots between carbs and engine that are hard like rock and have crack traces where clamps sit


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[jgger]

I hope that does it for you, it's ALWAYS the stupid stuff that bites me in the butt! Good luck.

[calj737]

Thanks everyone
It's boots between carbs and engine that are hard like rock and have crack traces where clamps sit

That will solve your surging RPMs, but that is not the reason #1 is cold.

[Can550]

It was not cold as not firing cold. It was blowing colder air compared to 3&4

Unless if 1 is not firing but will still blow air


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[calj737]

"Blowing colder air" is a pretty good indication of combustion differences. Compression will cause air to be expelled. Combustion produces heat in that exhausted air. Combustion problems are either spark or fuel.

It's up to you...

[Can550]

Thanks calj737
I shall check spark on #1 and contact at plug cover/ wire. I wish I could cut 1/4" end but it's already sitting at the edge. I removed cap and can see poor connectivity.

Is a spliced and wire extension recommended?


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[Can550]

Today everything is closed so couldn't get to buy parts and work on bike.

Measured apart plug caps (they are all 5k ohms) 1,2,4 measured between 4.79-5 k #3 is ZERO no resistance

Tomorrow will buy one but meantime excuse me being naive, what can this cause ?


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[calj737]

0 resistance would cause a poor spark. I'd say based upon your other replies, that you measured it incorrectly.

Please check the FUEL LEVEL in your carbs!

[Can550]

I did clear tube test and level sits about 2mm below bowl gasket.

My manual says to use DR7EA plugs D7EA for American bikes so guess 5k ohms caps are stock


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[calj737]

I did clear tube test and level sits about 2mm below bowl gasket.

Too high. Should be 2x that. What do the plugs look like?

[Can550]

Well plugs aren't the right picture now (a bit blackish) since bike was running on and off with insulators leaking, wrong timing etc.

If I didn't find new insulators tomorrow, considering to shrink wrap them what is the opinion on that if anyone has done before.

At the moment bike has D7EA but considering to buy a set of DR7EA since covers are 5k


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[Can550]

Just two days ago all slides were moving with throttle perfectly (carbs were cleaned and rebuilt) today put new plugs and insulators and #4 slide isn't moving at all. Stuck at the bottom. What should I check. Removed the top covers and I can see all remaining three have two arms that move with throttle, only one moves in #4 whereas the one with spring that is to lift slide, doesn't move rather prevents movement of others. Removed the screw from this one and remaining three moved freely.

Hope didn't damage anything while man handling install and don't have to remove carbs again


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[Can550]

Cannot forgive myself
Damaged #4 carb body. Pinched cylinder and slider is stuck.

Not sure if I can use body from an other CB or have to source only 550
Appreciate any help/ suggestion.


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[calj737]

What exact carb model (stamped on right side of #4 body, head side) do you have? Yes, you can swap a single carb and transfer your internals to the new body, or complete carb onto your rack.

There's ample spares around, but you'll often have to source it outside CA- 

[Can550]

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[754]

 If you can get the slide up, pushing from underneath....very carefully you can fix it... I think.
You will see a shiny spot where it is binding. Work that down carefully. 400 grit paper around a 1/2 rod would probably work. Worth a try, might take an hour, but gets your carbs working again.

[calj737]

You want PD46A carb bodies

[Can550]

Yes
When I'm putting needle clip on 3rd groove, is it 3rd from top or bottom?
Thanks


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