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Author Topic: Wont stay running.... help.  (Read 901 times)

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Offline Kalamazoo

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Wont stay running.... help.
« on: May 20, 2009, 05:03:42 PM »
My 1976 CB 550 will not stay running, it will run if I hold the throttle open a bit, but wont rev over 3500 rpms.
Just cleaned the carbs yesterday.
Its running on all 4, all pipes are hot.

I know for a fact it is running rich,  quite rich in fact.  Would that have anything to do with it?

Set points? Timing?

Thanks
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Offline khardrunner14

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Re: Wont stay running.... help.
« Reply #1 on: May 20, 2009, 05:12:15 PM »
Yeah it would. Did you check/set your float heights while you were in there? That would be my guess.
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Offline TwoTired

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Re: Wont stay running.... help.
« Reply #2 on: May 20, 2009, 05:13:22 PM »
It's always good to start with a complete and thorough tune up.

Air filter clean as new?

Have you done carbs before?  Did you clean the emulsion tubes?  Are you certain the slow jets are clear?  Did you check for corrosion blockage of the pilot circuit passageway?

Should we assume the bike is totally stock in configuration wither the stock part still attached?

Does it run with the choke lever down?  (Down = off)  Up is for cold start.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Kalamazoo

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Re: Wont stay running.... help.
« Reply #3 on: May 20, 2009, 05:34:27 PM »
checked float heights 22mm is correct yes?

Sorry sorry, I am running uni pods.---- I am running 115 mains, was told that would be correct but is obviously way off.

Emulsion tubes are clean, Slow jets clean, bike was just running the other day and I was driving.

Pilot circuit passage way.... I am new to carbs, Im going to need help on that one.

No it will not run with with choke in any position, and messing with the air mixture doesn't do anything.
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Offline TwoTired

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Re: Wont stay running.... help.
« Reply #4 on: May 20, 2009, 10:56:43 PM »
22mm is correct.

Running before but not now?  Is your fuel supply clean?  Could the carbs have become contaminated?

Might be that you are running so rich the the spark plugs are fouled.  Pull them out and have a look.  Black soot on the center electrode insulator can make the plugs misfire.

These mechanical slide carbs have three fuel metering devices; the slow jet/pilot circuit, the throttle valve on the slides, and the main jet.  Pilot circuit dominates from idle to about 1/4 throttle setting, throttle valve, 1/4 to 3/4 setting and the main for 3/4 to full open.  It's possible to maladjust/select each of the metering devices.

Assuming the carbs are indeed clean inside, you need to know your needle clip position and also any numbers found on the needles.   

Are your carbs F model or K model types?  There is a stamping on each carb body mount flange, top right.

The slow jet fits into a hole in the carb body, behind it is a passageway leading to an air jet, the air bleed adjust screw, and the exit hole into the throat of the carb.  One possibility is corrosion inside the passageway restricting flow.  Carb cleaners won't remove corrosion.  It can happen, it's not normal, but I have no idea what conditions your carbs have seen since 1976.  I only know that this circuit must be "proved" while rebuilding these carbs.

Cheers,

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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Hush

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Re: Wont stay running.... help.
« Reply #5 on: May 21, 2009, 12:51:25 AM »
I'm more basic thatn TT, do you have gas? in the tank? getting to the carbs?
Just a thought, lack of ability to rev says lack of gas to me..........but that's just me. :D
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Offline Kalamazoo

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Re: Wont stay running.... help.
« Reply #6 on: May 23, 2009, 12:15:24 PM »
Yes it was running before.

Just cleaned the tank, but I'm going to take off and clean again.

Plugs are fouled, had a feeling and will be replacing, however I am kind of putting it off because new plugs will just get fouled again with these jets, new jets are in order.

They are F model carbs.

Yes I have gas, haha already been thru that whole running out of gas ordeal, gas is reaching the carbs.


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