New pipes and high idle?
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,081
Likes: 2,159
From: Ohio
From a tuning standpoint, why did the idle change with new longer less restrictive pipes, will lowering the idle repair the reason why it changed, will idling heat be affected in the summer by not looking for the reason why the idle changed, awww maybe I'm just to picky, carry on my Evo buddies.
Intermediate
Joined: Apr 2010
Posts: 47
Likes: 0
From: Central Ohio
I agree with bagger.
less restrictive exhaust & filter makes it easier for the engine to pull & push air (it is just an air pump). So the air volume has increased but the fuel volume has stayed the same resulting in a lean condition... raising the idle speed. Just lowering the idle screw will not correct this. My GUESS would be about a 1/4- 1/2 turn counter-clockwise on the mixture screw should help if not cure this. plenty of reading on how to set mixture on here to be found but thats where Id start.
Wouldnt just lower the idle & go with it if it was mine....just sayin...
less restrictive exhaust & filter makes it easier for the engine to pull & push air (it is just an air pump). So the air volume has increased but the fuel volume has stayed the same resulting in a lean condition... raising the idle speed. Just lowering the idle screw will not correct this. My GUESS would be about a 1/4- 1/2 turn counter-clockwise on the mixture screw should help if not cure this. plenty of reading on how to set mixture on here to be found but thats where Id start.
Wouldnt just lower the idle & go with it if it was mine....just sayin...
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
The carb if an air/fuel mixing device. If the volume of air is increased, the volume of fuel will increase accordingly. If the density of air changes then the mixture will change. First set the idle at the speed it needs to be, then start with the idle air mixture screw set to 1.5-2 turns out. To set it if the lead plug isn't already drilled out you will need to carefully take a 1/8" drill and drill through the center of the lead plug. don't go too deep or you will damage the mixture screw. Next, take a sheet metal screw and put it into the lead plug , then work the lead plug out. now, gently screw the mixture screw in until it seats. Now you can turn it out to where you want it to be to start with. After you warm the engine up you can use the standard method to get the final setting. The one adjustment you may want to mqake is the Sporty needle, we dont change springs or drill the slides on most street builds as the power gain is minimal, but the mileage loss is noticeable.
Once you've done that put some fresh plugs in it and ride it normally for a while, then check your plugs. They should be a very light tan color. Todays unleaded fuels do not color up plugs like the older leaded fuels did. Don't go throwing in larger jets just because you changed a few things, yes harley's are a little lean to begin with but plug readings don't lie. Analyze and evaluate first, then make informed decisions and you will probably be happier with the results. Hope this helps
Once you've done that put some fresh plugs in it and ride it normally for a while, then check your plugs. They should be a very light tan color. Todays unleaded fuels do not color up plugs like the older leaded fuels did. Don't go throwing in larger jets just because you changed a few things, yes harley's are a little lean to begin with but plug readings don't lie. Analyze and evaluate first, then make informed decisions and you will probably be happier with the results. Hope this helps
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