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Author Topic: twin cv carb tuning?  (Read 1287 times)

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Offline muttblbc

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twin cv carb tuning?
« on: July 30, 2008, 02:56:07 PM »
ive been having a persistant problem with 70s twins. i can get the bike to idle nicely at 1100-1200 rpm, i take it for a ride stop at a stop light and the rpm gos up to about 3500 to 4000 and wants to idle there. if i slowly let out the clutch to right at the point it engages the rpms will lower back down to 1100 or 1200. is this the carbs or the clutch? anyone know the remedy?
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fixahonda

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Re: twin cv carb tuning?
« Reply #1 on: July 30, 2008, 03:54:33 PM »
It sounds like the throttle is hanging up somehow. I would make sure the cable is routed so it's not turning any sharp corners. Try to turn the bars to the stops either way when it's hanging up and see if it changes.
Otherwise I don't know why it would do what you are describing. The clutch being out of adjustment would cause hard shifting and a host of other problems.

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Offline muttblbc

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Re: twin cv carb tuning?
« Reply #2 on: July 30, 2008, 04:20:21 PM »
its not the cables, Ive checked those repeatedly,
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Offline scunny

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Re: twin cv carb tuning?
« Reply #3 on: July 30, 2008, 04:26:26 PM »
sounds like a carb problem. try spraying wd40 round the carb boots to see if there is a leak(rpms will change) CV carbs can be finicky about vacuum
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Offline muttblbc

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Re: twin cv carb tuning?
« Reply #4 on: July 30, 2008, 04:44:44 PM »
tried that one too. ive been through the idle circuit several times, verified that the correct jets are in place, the air cleaners are new. just not sure what to check next.
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Offline mark

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Re: twin cv carb tuning?
« Reply #5 on: July 30, 2008, 05:34:02 PM »
You may also want to check ignition timing and to verify that the advancer is not sticking in the 'advanced' position.
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Offline tbpmusic

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Re: twin cv carb tuning?
« Reply #6 on: July 30, 2008, 05:51:20 PM »
Quote from: muttblbc on July 30, 2008, 02:56:07 PM
ive been having a persistant problem with 70s twins. i can get the bike to idle nicely at 1100-1200 rpm, i take it for a ride stop at a stop light and the rpm gos up to about 3500 to 4000 and wants to idle there. if i slowly let out the clutch to right at the point it engages the rpms will lower back down to 1100 or 1200. is this the carbs or the clutch? anyone know the remedy?

I assume you're talking about a 350 or 450 ???
You always need to state the year and model if you want help.

At any rate, in light of the info you've given, sounds like the carbs are not synched up.


bill2
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Offline muttblbc

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Re: twin cv carb tuning?
« Reply #7 on: July 30, 2008, 07:13:35 PM »
sorry, itsa 71 cb350
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Offline TomC

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Re: twin cv carb tuning?
« Reply #8 on: July 30, 2008, 07:25:46 PM »
Hi Muttblbc
     I had a similar problem with my CB450 thirty years ago or so. It was carb. balance. I balanced the carbs. and it went away. Maybe only 2500rpm thou.
          TomC in Ohio
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Offline miles nowhere

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Re: twin cv carb tuning?
« Reply #9 on: July 31, 2008, 08:15:39 AM »
sounds kinda familiar, come to think of it...mine didn't start doing it until  you touched it....coincidence? I think not! :P
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Offline muttblbc

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Re: twin cv carb tuning?
« Reply #10 on: July 31, 2008, 04:29:37 PM »
its not not coincidence.
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