Shovelhead A place to talk about Shovelheads.

Isolated primary

Thread Tools
 
Search this Thread
 
Old Mar 14, 2023 | 06:35 PM
  #1  
76HDflh's Avatar
76HDflh
Thread Starter
|
Cruiser
Photogenic
Liked
Joined: Jun 2021
Posts: 116
Likes: 41
From: New Jersey
Default Isolated primary


Sorry to ask, must be tired of answering questions about this. According to the diagram Bottom line on back of motor says to leave open to the atmosphere, do you attach a short piece of hose and leave it open. Is there a filter or something you put at the end of the hose? I’m guessing this is the crankcase vent?
Thank you for any help.
 
Reply
Old Mar 15, 2023 | 06:59 AM
  #2  
tld6008's Avatar
tld6008
Cruiser
5 Year Member
Liked
Loved
Community Favorite
Joined: Sep 2020
Posts: 222
Likes: 77
From: Gulf Breeze
Default

Yes most attach hose and run it back and off to right side You can see mine in photo


 
Reply
Old Mar 15, 2023 | 07:24 AM
  #3  
Dan89FLSTC's Avatar
Dan89FLSTC
Seasoned HDF Member
Veteran: Navy
Active Streak: 30 Days
Top Answer: 3
Top Answer: 5
Joined: May 2008
Posts: 21,146
Likes: 12,713
From: South Carolina
Default

No need for a filter.
 
Reply
Old Mar 15, 2023 | 09:33 AM
  #4  
carpenter_93inch's Avatar
carpenter_93inch
Novice
Joined: Feb 2023
Posts: 21
Likes: 12
From: MO
Default

The same on my 77 super glide, I went a little further, installed a catch can, just can not remember from were I obtained it. But it has a filter screwed on the top just another conversation piece when looked at, " what the hell is that for?"
 
Reply
Old Mar 15, 2023 | 09:48 AM
  #5  
84 Shovel's Avatar
84 Shovel
Cruiser
Photogenic
Joined: Jan 2023
Posts: 146
Likes: 170
From: chicagoland
Default

I ran it to the left side and extended it with a metal tube so it blows on the rear chain.
 
Reply
Old Mar 15, 2023 | 04:23 PM
  #6  
76HDflh's Avatar
76HDflh
Thread Starter
|
Cruiser
Photogenic
Liked
Joined: Jun 2021
Posts: 116
Likes: 41
From: New Jersey
Default Isolated primary

Thanks, I guess I suffered a brain fart when isolating the primary. Did everything required but blocked off both holes on rear of engine block. I got concerned about pressure buildup and revisited my work and the above diagram. Good thing this is a labor of love, 2 steps forward 1 step back!

This is my project 1976 FLH.
 
Reply
Old Mar 16, 2023 | 09:33 AM
  #7  
ShovelEd's Avatar
ShovelEd
Club Member
Joined: Jun 2010
Posts: 14,212
Likes: 63,866
From: Other Side of the Tracks
Default

I run a filter at the end of my crankcase breather hose.

YMMV


 
Reply
Old Mar 16, 2023 | 09:52 AM
  #8  
76HDflh's Avatar
76HDflh
Thread Starter
|
Cruiser
Photogenic
Liked
Joined: Jun 2021
Posts: 116
Likes: 41
From: New Jersey
Default Isolated primary

Does the hose dead end there? Is the purpose to collect mist from crankcase through one inlet then exit to atmosphere through the other? I’m guessing the oil filter mount has 2 fittings.
 
Reply
HD Forum Stories

The Best of Harley-Davidson for Lifelong Riders

story-0

7 Times Harley-Davidson Chucked Tradition Out the Window

 Verdad Gallardo
story-1

7 Surprising Harley-Davidson Products that Are Not Motorcycles

 Verdad Gallardo
story-2

8 Best Harley-Davidson Motorcycles Ever

 Pouria Savadkouei
story-3

10 Worst Harley-Davidson Motorcycles Ever

 Pouria Savadkouei
story-4

Killer Custom's Jail Break Is The Breakout That Refused to Blend In

 Verdad Gallardo
story-5

Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?

 Verdad Gallardo
story-6

Harley-Davidson Reveals Super Cool Cafe Racer Concept

 Verdad Gallardo
story-7

Engraved Rebellion: Inside Bundnerbike's Glam Rock II

 Verdad Gallardo
story-8

10 Motorcycles You Should Never Buy

 Joe Kucinski
story-9

10 Things Harley-Davidson Needs to Fix in 2026

 Verdad Gallardo
Old Mar 16, 2023 | 01:13 PM
  #9  
ShovelEd's Avatar
ShovelEd
Club Member
Joined: Jun 2010
Posts: 14,212
Likes: 63,866
From: Other Side of the Tracks
Default

Originally Posted by 76HDflh
Does the hose dead end there? Is the purpose to collect mist from crankcase through one inlet then exit to atmosphere through the other? I’m guessing the oil filter mount has 2 fittings.
That is a small crankcase vent filter. 😉





 

Last edited by ShovelEd; Mar 16, 2023 at 01:15 PM.
Reply
Old Mar 16, 2023 | 03:49 PM
  #10  
76HDflh's Avatar
76HDflh
Thread Starter
|
Cruiser
Photogenic
Liked
Joined: Jun 2021
Posts: 116
Likes: 41
From: New Jersey
Default Isolated primary

ShovelEd, thanks for the info, looks good, will start tracking one down.
 
Reply



All times are GMT -5. The time now is 04:58 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