Softail Models Standard, Custom, Night Train, Deuce, Springer, Heritage, Fatboy, Deluxe, Rocker and Cross Bones.
Sponsored by:
Sponsored by:

Mikuni Question

Thread Tools
 
Search this Thread
 
Old Aug 16, 2014 | 04:41 PM
  #1  
olongapo1's Avatar
olongapo1
Thread Starter
|
Road Master
Joined: Oct 2008
Posts: 970
Likes: 19
From: Philippines
Default Mikuni Question

I've worked on a lot of bikes that have Mikuni Carbs, have a Mikuni on my Train and rebuilt several 42's. I consider myself a knowledgeable wrench but there is a port on the Mikuni which I cannot identify its purpose. The port is illustrated with a yellow pencil in the attached photo. It is Not the vacuum port for the petcock, Not the float bowl overflow, and of course Not the fuel inlet. I have a Mikuni tuning and rebuild manual but this port is not shown or mentioned.

My first thought is that it's an extra vacuum port which should be plugged if not utilized however on all Mikuni's I've seen installed on bikes, this port is always open (Unplugged).

Can anyone identify this port and its purpose?
 
Attached Thumbnails Mikuni Question-img_0604.jpg  
Reply
Old Aug 17, 2014 | 07:56 PM
  #2  
olongapo1's Avatar
olongapo1
Thread Starter
|
Road Master
Joined: Oct 2008
Posts: 970
Likes: 19
From: Philippines
Default

No responses from this forums site but I was able to find a bit more info googling. For the minority, Old School boys who learned to wrench during the carburetor age, the port is an air vent and must remain (Unplugged). See the 2 attachments.
 
Attached Thumbnails Mikuni Question-image.jpg   Mikuni Question-image-2.jpg  
Reply
Old Aug 19, 2014 | 06:29 AM
  #3  
oct1949's Avatar
oct1949
Club Member
15 Year Member
Liked
Loved
Joined: May 2007
Posts: 145,895
Likes: 821
From: 40 miles Northeast of Indy..
Default

Haven't had a Mikuni on a bike since 73. a lot better than the old Tills that was stock, but I've forgotten most of what I knew about working on them..

Glad you found you answer..
 
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
DDS114
Touring Models
14
Apr 1, 2019 05:56 PM
biglady112
Blowers/Turbos/Nitrous Oxide
15
Mar 11, 2013 06:41 AM
mustangwagz
Ironhead
22
Nov 25, 2010 06:38 AM
Johnnyiroc
General Harley Davidson Chat
6
Apr 13, 2010 09:11 AM
ReddRidder2003
Exhaust System Topics
5
Jul 7, 2008 01:24 AM




All times are GMT -5. The time now is 07:23 PM.

story-0
7 Times Harley-Davidson Chucked Tradition Out the Window

Slideshow: Harley-Davidson built its reputation on nostalgia, but every so often, the company took a hard left turn into the future.

By Verdad Gallardo | 2026-05-20 11:18:19


VIEW MORE
story-1
7 Surprising Harley-Davidson Products that Are Not Motorcycles

Slideshow: The bar-and-shield logo shows up on far more than motorcycles, some of the company's most unexpected products have nothing to do with riding.

By Verdad Gallardo | 2026-04-29 16:50:35


VIEW MORE
story-2
8 Best Harley-Davidson Motorcycles Ever

Slideshow: Not every Harley gets it right, but these are the ones that genuinely earned their reputation.

By Pouria Savadkouei | 2026-04-15 14:23:21


VIEW MORE
story-3
10 Worst Harley-Davidson Motorcycles Ever

Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.

By Pouria Savadkouei | 2026-04-01 20:01:09


VIEW MORE
story-4
Killer Custom's Jail Break Is The Breakout That Refused to Blend In

Slideshow: Killer Custom's "Jail Breaker" build focuses more on stance and visual aggression than mechanical overhaul.

By Verdad Gallardo | 2026-03-18 19:20:32


VIEW MORE
story-5
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?

Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.

By Verdad Gallardo | 2026-03-07 16:15:30


VIEW MORE
story-6
Harley-Davidson Reveals Super Cool Cafe Racer Concept

Slideshow: Harley-Davidson's new RMCR concept revives the café racer formula with modern hardware-and it may be exactly the reset the company needs.

By Verdad Gallardo | 2026-03-04 12:23:37


VIEW MORE
story-7
Engraved Rebellion: Inside Bundnerbike's Glam Rock II

Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.

By Verdad Gallardo | 2026-02-24 18:19:44


VIEW MORE
story-8
10 Motorcycles You Should Never Buy

Slideshow: There is no shortage of great motorcycles to buy, but we would avoid these ten.

By Joe Kucinski | 2026-02-19 14:50:51


VIEW MORE
story-9
10 Things Harley-Davidson Needs to Fix in 2026

Slideshow: Harley-Davidson's challenges aren't abstract; they show up in dropping shipments, shrinking dealer traffic, and strategic decisions that aren't yet translating into growth.

By Verdad Gallardo | 2026-01-13 18:33:17


VIEW MORE