Idle Question
Thread Starter
|
Cruiser
Joined: Feb 2009
Posts: 239
Likes: 2
From: California
Idle Question
Always wondered why when I first start my bike (98 FXST, engine stock except exhaust and air filter), why does it idle like it has a cam while cold, and then smooth out when warm?
Outstanding HDF Member
Joined: Oct 2010
Posts: 2,706
Likes: 14
From: Near Frankenmuth, MI
I'm guessing carbed because EFI when working correctly chokes the bike precisely as needed and from my experience they do not have "cold start" issues or odd lulling / lopping that can occur with manual adjustable carbs.
A richened condition while choking a carbed bike feeds enough gas to keep it running as it warms. This causes the high idle to engage so you have a motor warming at a fast enough speed to keep it going while cold.
Of course once warmed, or as it's warming it begins to either die out from too much choke, or the idle speed increases, and then will decrease from the over-enriched condition from the choke. Metering off the choke as it warms, smooths out the idle and let's you know it's ready to go.
So when cold it does have a "lulling / lopping" or hesitating sound similar to the sound of an aftermarket cam.
A richened condition while choking a carbed bike feeds enough gas to keep it running as it warms. This causes the high idle to engage so you have a motor warming at a fast enough speed to keep it going while cold.
Of course once warmed, or as it's warming it begins to either die out from too much choke, or the idle speed increases, and then will decrease from the over-enriched condition from the choke. Metering off the choke as it warms, smooths out the idle and let's you know it's ready to go.
So when cold it does have a "lulling / lopping" or hesitating sound similar to the sound of an aftermarket cam.
Stellar HDF Member
Joined: May 2009
Posts: 2,856
Likes: 127
From: Middle of Kansas
I changed the pilot jet from a 42 to a 45 on my 99 FXSTC. I now start it with the enrichner pulled out, and after a few seconds push it all the way in, and use the throttle lock to keep it at a good idle. It sounds much better at idle both cold and hot.
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
First check for air leaks,don't forget the vacuum hoses. Then make sure that the enrichner cable is fully seated in the carb. Ensure that all the throttle cables/linkage/etc are not sticking. If all is well there then try going larger in the pilot jet, and turn the idle mixture screw 2 1/2-3 turns out from being seated gently. (Disclaimer: That is if all other mechanical and electrical components are functioning properly.) Hope this helps.
Trending Topics
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
Likes: 1,524
From: Coromandel Peninsula New Zealand
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
Jason Momoa Is Turning Classic Harleys Into PHEVs
Verdad Gallardo
Harley-Davidson Fat Boy Becomes a Dark, Decepticon-Inspired Custom
Verdad Gallardo
6 Weirdest Harley-Davidsons Ever Sold to the Public
Verdad Gallardo
7 Times Harley-Davidson Chucked Tradition Out the Window
Verdad Gallardo
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Thread
Thread Starter
Forum
Replies
Last Post
chucktowndcroz
Primary/Transmission/Driveline/Clutch
6
Sep 28, 2010 07:41 PM