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Offline Spikeybike

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this a new one (carb problem)
« on: May 11, 2008, 03:53:29 pm »
i finally got the phoenix up and running and now here's my new problem I've never encountered before

when the bike warms up it, the rpms stay at around 3k at idle ???
throttle screw backed off completely, cables not stuck, idle jets are stock, jet needle position is stock,
  I'm lost i dont get it
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Offline Gordon

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Re: this a new one (carb problem)
« Reply #1 on: May 11, 2008, 04:18:07 pm »
Is the throttle cable adjusted too tight, as in it's not letting the slides close completely?  Have the carbs been balanced?
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Offline TwoTired

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Re: this a new one (carb problem)
« Reply #2 on: May 11, 2008, 04:33:53 pm »
Do the individual carb height adjusters allow the slides to close completely when the idle knob is backed off?  Did you use the drill bit method for carb Sync?

Do the throttle cables block throttle closure?

Do you have vacuum leaks between carb and cylinder head?

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
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Offline Spikeybike

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Re: this a new one (carb problem)
« Reply #3 on: May 11, 2008, 05:27:28 pm »
Quote from: Gordon on May 11, 2008, 04:18:07 pm
Is the throttle cable adjusted too tight, as in it's not letting the slides close completely?  Have the carbs been balanced?

the lock nut had vibrated off the pull cable but this shouldn't have caused that, put that back on ,problem's still there

Quote from: TwoTired on May 11, 2008, 04:33:53 pm
Do the individual carb height adjusters allow the slides to close completely when the idle knob is backed off?  Did you use the drill bit method for carb Sync?
the height adjusters "looked" to be doing there job properly.
used drill bit then "needle/gauge" style sync tool (witch i hate, i might add)
 
Quote from: TwoTired on May 11, 2008, 04:33:53 pm

Do you have vacuum leaks between carb and cylinder head?

all the manifold screws are there, and the o-rings are new. the manifold rubbers were in better shape then my old ones before the fire
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Offline TwoTired

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Re: this a new one (carb problem)
« Reply #4 on: May 11, 2008, 05:43:48 pm »
Quote from: spikeybike on May 11, 2008, 05:27:28 pm
Quote from: TwoTired on May 11, 2008, 04:33:53 pm
Do the individual carb height adjusters allow the slides to close completely when the idle knob is backed off?  Did you use the drill bit method for carb Sync?
the height adjusters "looked" to be doing there job properly.
used drill bit then "needle/gauge" style sync tool (witch i hate, i might add)

Kinda side stepped the issue there, Spikey.  You decide if this is part of your carb problem.  Is your current problem new, or has it been there since your last drill bit sync?

The drill bits keep the slides from closing fully.  If all the individual adjusters are skewed equally, you can achieve carb sync and even vacuum sync later.  But, the slide travel can be limited by skewed adjusters and not let the slides close down to where the need to be at warm idle.

You should look inside the carb throats with a flashlight and see if the slides will fully close with the idle knob backed out and the throttle cables disconnected.  If not, then you get to do the re-synch over again.

This is one reason why I don't care for the drill bit method, btw.  I adjust each one until light won't pass at each carb slide (off the bike), then vacuum sync with the running bike.

Cheers,



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Lloyd... (SOHC4 #11 Original Mail List)
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Offline mattcb350f

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Re: this a new one (carb problem)
« Reply #5 on: May 11, 2008, 05:50:25 pm »
How about the choke/high idle adjustment set up? maybe that bit is holding it open too.

 Matt.
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Offline TwoTired

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Re: this a new one (carb problem)
« Reply #6 on: May 11, 2008, 05:58:08 pm »
Quote from: mattcb350f on May 11, 2008, 05:50:25 pm
How about the choke/high idle adjustment set up? maybe that bit is holding it open too.

 Matt.

The F model 550's don't have that.  Only Cb550K models in 77-78 had that feature.

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

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Offline Spikeybike

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Re: this a new one (carb problem)
« Reply #7 on: May 11, 2008, 06:46:19 pm »
Quote from: TwoTired on May 11, 2008, 05:43:48 pm
Quote from: spikeybike on May 11, 2008, 05:27:28 pm
Quote from: TwoTired on May 11, 2008, 04:33:53 pm
Do the individual carb height adjusters allow the slides to close completely when the idle knob is backed off?  Did you use the drill bit method for carb Sync?
the height adjusters "looked" to be doing there job properly.
used drill bit then "needle/gauge" style sync tool (witch i hate, i might add)

Kinda side stepped the issue there, Spikey.  You decide if this is part of your carb problem.  Is your current problem new, or has it been there since your last drill bit sync?

The drill bits keep the slides from closing fully.  If all the individual adjusters are skewed equally, you can achieve carb sync and even vacuum sync later.  But, the slide travel can be limited by skewed adjusters and not let the slides close down to where the need to be at warm idle.

You should look inside the carb throats with a flashlight and see if the slides will fully close with the idle knob backed out and the throttle cables disconnected.  If not, then you get to do the re-synch over again.

This is one reason why I don't care for the drill bit method, btw.  I adjust each one until light won't pass at each carb slide (off the bike), then vacuum sync with the running bike.

Cheers,





i actually thought that, when i was doing it. but then thought "why would people do it if it just messed up other stuff down the line"

i'll have to get the carbs off and change that ,
i'm fairly certain that's the problem, thanx TT
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