WTF is this???
WTF is this???
So, I was riding around town today and decided to stop at a gas station for a pack of smokes and something to quench my thirst. When I got done, I jumped back on the EG, and attempted to fire it up. It backfired through the intake!! Never done that before. After that, I hit the switch again and she started no problem, but it started whistling from somewhere around the throttle body. I got it home, and took off the intake and began to look around, and when I did, I found a rubber cap that had to come from somewhere. This is the only place I could think that it is supposed to go, but I am not totally sure.
Extreme HDF Member
Joined: Aug 2012
Posts: 11,392
Likes: 184
From: Big ol Titties
That is where a line plugs into the TB from bikes with a charcoal canister. Some guys actually leave it open when they take the can off most just plug it with a standard vacuum plug. It really doesn't change the way it runs open or closed.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
if open, then uncontrolled air into intake, no?
I like my air filtered and measured by a sensor
mike
I like my air filtered and measured by a sensor
mike
Trending Topics
Outstanding HDF Member
Joined: Nov 2012
Posts: 2,422
Likes: 14
From: Fla
A vacuum leak is a vacuum leak...
no matter what 'everyone' else does. Maybe you wouldn't notice the difference, but there IS a difference. That whistle the OP heard was one such difference, as well as the unfiltered air entering the engine, and slightly less vacuum inside the intake manifold as long as it remains open.
Yes, that is where the cap goes. It popped off when the engine backfired. Every now and then, be sure to check it. Mine keeps getting cracks in it, from dry rot I imagine, so I have to replace it every year or so.
no matter what 'everyone' else does. Maybe you wouldn't notice the difference, but there IS a difference. That whistle the OP heard was one such difference, as well as the unfiltered air entering the engine, and slightly less vacuum inside the intake manifold as long as it remains open.
Yes, that is where the cap goes. It popped off when the engine backfired. Every now and then, be sure to check it. Mine keeps getting cracks in it, from dry rot I imagine, so I have to replace it every year or so.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
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
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Extreme HDF Member
Joined: Aug 2012
Posts: 11,392
Likes: 184
From: Big ol Titties
Ya I Like mine filtered too, no way I'll run a 1/4" wide open hole in my TB. Like I said though some guys do it, just makes me scratch my head when you think about how little time and effort it takes to plug.
