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Author Topic: #1 not running on idle  (Read 1533 times)

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Offline OneWheelDrive

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#1 not running on idle
« on: April 11, 2011, 09:36:51 AM »
Soooooo I've been trying desperately to diagnose a cold #1 pipe at idle.  '74 550k with 022A carbs.  What I've done so far is pull the float bowl off, check the fuel height, check the float level, pull both the pilot jet and main jet and check that they're clear with guitar string.   When the jets were off I blew the passageways with compressed air to make sure they were clear.

I also switched the 1 and 4 plugs and wires and #4 was still running as it should.  Plug chop shows a dry white plug so I know I'm not getting fuel.  She runs great above 1/4 throttle, but won't spray fuel below that.  Is there anything else that could be clogged that would result in a fuel delivery problem?
« Last Edit: April 11, 2011, 03:21:18 PM by OneWheelDrive »
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline RickB

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Re: #1 not running on idle
« Reply #1 on: April 11, 2011, 10:18:35 AM »
I have a similar problem that I believe is due to my Dyna ignition not getting enough power at low RPM's from my alternator and hence, my plug miss-behaving.

Although you're saying your cylinder isn't even getting fuel. Are you noticing any fuel leaking out your pipe? What about your air filter? Is that wet? Could fuel be blowing back out the other way? That happens on my CB400F, through the airbox.

You're sure that carb is getting fuel? Have you opened the bowl drain plug to verify that carb is actually getting fuel?

After that I would think that could perhaps your slide be stuck in the throat of that carb? If all your jets and emulsion tubes are clear, what else could it be? I'm out of my depth already!
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Offline OneWheelDrive

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Re: #1 not running on idle
« Reply #2 on: April 11, 2011, 10:30:53 AM »
Like I said, bowl has fuel, plug has spark, above idle, bike runs great so it's not the slide.  Problem is idle only fuel delivery problem.
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline midnightrider

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Re: #1 not running on idle
« Reply #3 on: April 11, 2011, 10:37:40 AM »
Is this a new development? 

Have you hooked the carbs up to a vacuum gauge? (or carb syncer) 
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Offline OneWheelDrive

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Re: #1 not running on idle
« Reply #4 on: April 11, 2011, 10:52:04 AM »
Quote from: midnightrider on April 11, 2011, 10:37:40 AM
Is this a new development? 

Have you hooked the carbs up to a vacuum gauge? (or carb syncer) 


Yes new development.  I did hook the #1 and #2 carbs intakes up to my vacuum gauge and although they were not exactly even as there was no combustion in #1, it was still pulling nearly the same reading so it SHOULD be pulling fuel through the jets...
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
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Offline TwoTired

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Re: #1 not running on idle
« Reply #5 on: April 11, 2011, 11:25:19 AM »
Still sounds like a pilot circuit issue.

There are four exits to the pilot circuit in the carb.
The pilot jet
The air jet
The air bleed screw hole
The exit port into the carb throat.
 Did you see air exit/enter each of these ports?
That's why I use aerosol carb cleaner to "prove" passage to each and every exit of the pilot circuit.


I will mention that a slide too closed, compared to the the other three, will cause a dead cylinder at idle position.

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 OneWheelDrive

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Re: #1 not running on idle
« Reply #6 on: April 11, 2011, 11:30:18 AM »
Quote from: TwoTired on April 11, 2011, 11:25:19 AM
Still sounds like a pilot circuit issue.

There are four exits to the pilot circuit in the carb.
The pilot jet
The air jet
The air bleed screw hole
The exit port into the carb throat.
 Did you see air exit/enter each of these ports?
That's why I use aerosol carb cleaner to "prove" passage to each and every exit of the pilot circuit.


I will mention that a slide too closed, compared to the the other three, will cause a dead cylinder at idle position.

Cheers,


Hooray for TT!  I love seeing your replies to my questions.  I did use aerosol cleaner to blast the pilot circuit, both from the screw adjust side with the screw out, and the pilot jet side with the jet out.  I couldn't verify from the carb exit side as the rack was on the bike.  I'll pull the slide from the top and make sure the passageway is clear.

I suppose it could be a slide adjustment issue, I did adjust the carbs about two weeks ago and the nut may have come loose allowing the slide to drop.  I'll check it.
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline OneWheelDrive

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Re: #1 not running on idle
« Reply #7 on: April 11, 2011, 02:56:54 PM »
Surprise surprise, TT was dead on it.  It wasn't a fuel delivery problem at all.  The adjustment nut on #1 carb had indeed loosened and the slide had dropped, killing the cylinder at idle.  I quickly raised the slide to get it running and viola!  Although it's slightly out of sync now, it's running on all four.  I'll take the time to re-sync when I've got some time.  Thanks TT!

I have had a tough time tightening the 8mm nuts without changing the adjustment setting.  Anyone have an easy trick to do so?  I would use an open wrench to tighten while holding the flathead steady, but I can't get the wrench in there. 
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline Duanob

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Re: #1 not running on idle
« Reply #8 on: April 11, 2011, 03:14:14 PM »
it's an epidemic. All the bikes being taken out of winter storage sitting with old gas in the bowls. Then take a pilot jet with a hole you couldn't put a blonde C-hair through and you get easily plugged slow jets. I just had that happen on two carbs. Just fixed the #3 carb today. I also drained the tank completely, put in some fresh gas with a few splashes of Seafoam hoping to avoid this problem again. 
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Offline OneWheelDrive

  • A journey of 1000 miles starts with your first carb overhaul.
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Re: #1 not running on idle
« Reply #9 on: April 11, 2011, 03:16:01 PM »
Lucky for me the bike has been ridden all winter  8) The benefits of living in sunny So. Cal.!
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline TwoTired

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Re: #1 not running on idle
« Reply #10 on: April 11, 2011, 04:43:40 PM »
Quote from: OneWheelDrive on April 11, 2011, 02:56:54 PM
Thanks TT!
You're welcome.  Glad you got it sorted out!

Quote from: OneWheelDrive on April 11, 2011, 02:56:54 PM
I have had a tough time tightening the 8mm nuts without changing the adjustment setting.  Anyone have an easy trick to do so?  I would use an open wrench to tighten while holding the flathead steady, but I can't get the wrench in there.
You have to anticipate where the adjustment will be after tightening.  It's a trick made easier with certain tools.
 
I made the one below from an ordinary box end wrench using an Oxy Acetylene torch and a vise.  If I lost it, I'd make a new one.

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.
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