idle goes up
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Road Warrior
Joined: Sep 2006
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From: nj
idle goes up
I have a early 84 ironhead with a s&s carb the idle goes up when she is warmed up I did check the cables where they enter the carb to see if they are sticking they return and touch the idle screw. I checked the intake for leaks with propane and no change in rpm. Is there anything in the carb could be giving this poblem Thanks for your help.
Tourer
Joined: Jul 2009
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From: Minnesota
I was thinking the same thing, that sounds normal to me. When I start mine I give the idle speed screw a half turn in to help it idle better when doing a cold start. Then after it warms up I have to turn it back down of course. If I didn't turn it in before starting I'm sure it would just barely idle if at all without having to keep dicking with it, so I just start with a fast idle.
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Road Warrior
Joined: Sep 2006
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From: nj
Something sounds funny I start the bike and sounds okay when she is cold and is warm after she gets hot the idle goed up I feather the clutch in gear pull the clutch in and she goes back down. If i am sitting there and give the bike gas let the throttle go the idle is up hard to get it back down the throtle body where the cables connect looks like they are back but I did notice that there is 1 spring on the throttle return(2 cables) where the cable connects maybe not tight enough Thanks
The idle mixture screw [AKA the pilot screw] and the idle speed must be set when the engine is at full operating temperature. Then, when you start the bike cold, you have to work the throttle to keep it idling, but when it warms up it will be correct. This is the way it is supposed to work.
If you set it up when hot, then the idle speed changes as it warms up, the usual cause is intake leaks.
If you set it up when hot, then the idle speed changes as it warms up, the usual cause is intake leaks.
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Road Warrior
Joined: Sep 2006
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From: nj
Okay when she is cold your right the bike needs some throttle to keep her goin. As she gets warmed up she is fine after riding around and she gets hot that is where the idle goes up then I adjust it back down then. The bike starts up fine 2 squirts of throttle lift choke half way and she starts right up . Push the enricher back down set the throttle lock screw to keep it goin and that is it,.
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Road Captain
Joined: Nov 2005
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I have a early 84 ironhead with a s&s carb the idle goes up when she is warmed up I did check the cables where they enter the carb to see if they are sticking they return and touch the idle screw. I checked the intake for leaks with propane and no change in rpm. Is there anything in the carb could be giving this poblem Thanks for your help.
Possibly the cables need lube, could be hanging up a bit.
Last edited by peppi; Nov 29, 2010 at 03:54 PM.
Tourer
Joined: Apr 2010
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Well, where to start.
When you say S+S carb, what type?
Assuming that you are not using any form of choke/enrichner after starting, it would seem reasonable that the idle would be a little higher when the engine reaches operating temperature, especially if you have set the speed initially when the engine was a little cold still.
Are you saying there is an external return spring? Or are you referring to the small spring on the return cable itself, which has nothing to do with throttle return?
If there is some butterfly shaft wear, you can certainly get an undesirable idle speed variation.
A worn mechanical advance unit is a likely place for increased idle symptoms as well.
When you say S+S carb, what type?
Assuming that you are not using any form of choke/enrichner after starting, it would seem reasonable that the idle would be a little higher when the engine reaches operating temperature, especially if you have set the speed initially when the engine was a little cold still.
Are you saying there is an external return spring? Or are you referring to the small spring on the return cable itself, which has nothing to do with throttle return?
If there is some butterfly shaft wear, you can certainly get an undesirable idle speed variation.
A worn mechanical advance unit is a likely place for increased idle symptoms as well.