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post #1 of 5 (permalink) Old 12-30-2011, 02:42 PM Thread Starter
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Idle much better now

As you may recall my rear cylinder was flooding out at idle. Based on the advice from here and from Steve Reed and drained the rear carb float and then used a tiny straw to flush carb cleaner up into the float bowl, soak, and drain several times. Afterwards it was a bit difficult to start but once it did it was idling on the rear cylinder again!!!
I then took it out on a very short ride, but enough to fully warm it up. It seemed to run fine. The only issue I'm seeing now though is that it's now hunting for idle. Fully warmed it would hold idle for about 30 seconds, then surge up 500RPM for a bit, then settle back down. Its not done this before. Could this be from the float cleaning or a result of the very high concentration of sea foam and left over Stabil in the fuel? Perhaps I just need to take it out for a real ride after the float cleaning.

-Robert
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post #2 of 5 (permalink) Old 12-30-2011, 04:54 PM
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I would say sea foam it and run it. Run it a lot.

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post #3 of 5 (permalink) Old 12-30-2011, 06:38 PM
If only it had 6th gear..
 
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Not clear.. up to 500? Do u mean up to 5k or chugging down to 500 (would it even run?). If it's dropping way down I agree with niterider. If it's surging up I would check for air leaks.

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post #4 of 5 (permalink) Old 12-30-2011, 07:11 PM Thread Starter
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Surging as in I set it at 1200 and it will occasionally go up to 1600 or so. The symptoms are similar to an air leak but this just started after flushing my float so I'm thinking its unlikely that I happened to get an air leak at the exact same time.

-Robert

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Originally Posted by DavesVulster View Post
Not clear.. up to 500? Do u mean up to 5k or chugging down to 500 (would it even run?). If it's dropping way down I agree with niterider. If it's surging up I would check for air leaks.
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post #5 of 5 (permalink) Old 12-31-2011, 12:10 AM
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This sounds like a diaphragm issue. An air leak is generally constant. The slides may be moving while the engine is idling. Even with everything perfect, it is much more difficult to get a really smooth idle with a CV carb than a real carb, because the diaphragm setup is too sensitive.

One thing you have to remember, is that when idle speed changes up and down, something in there IS moving. It is not likely the throttle, as it has a pretty strong spring on it. Make sure you have a consistent supply of fuel to the carb. Remove the pilot screws and spray some carb cleaner in there, then put them back at about 2 1/2 turns out. A too lean (or too rich) idle air/fuel mixture will cause a fluctuation at idle, but not 500 rpm. It is also possible that you still have a intermittent problem with the needle valve. It would be interesting to hook up an emissions analyzer to it and watch it as the idle goes up and down. BTW, what kind of carb cleaner did you use? I use Gumout for carb cleaning once the carbs are apart, but any type of keytone based carb cleaner like Gumout can damage plastic and rubber parts, especially if you soaked them in it. Seafoam on the other hand is harmless to plastic and metal. You can get it in a spray can with a straw.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
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