General Harley Davidson Chat Forum to discuss general Harley Davidson issues, topics, and experiences.
Sponsored by:
Sponsored by:

Carbon build-up

Thread Tools
 
Search this Thread
 
Old May 13, 2017 | 08:00 PM
  #1  
Road Star's Avatar
Road Star
Thread Starter
|
Seasoned HDF Member
Veteran: Marine Corps
10 Year Member
Liked
Top Answer: 1
Joined: Dec 2012
Posts: 6,673
Likes: 502
From: Orange County
Default Carbon build-up

Hetes the pistons after about 10k miles. Does this look excessive?

 
Reply
Old May 13, 2017 | 08:03 PM
  #2  
Mr.Softy's Avatar
Mr.Softy
Seasoned HDF Member
Veteran: Air Force
15 Year Member
Liked
Community Favorite
Joined: Jul 2009
Posts: 5,023
Likes: 1,352
From: Virginia
Default

what octane and gas do you use?
 
Reply
Old May 13, 2017 | 08:25 PM
  #3  
Road Star's Avatar
Road Star
Thread Starter
|
Seasoned HDF Member
Veteran: Marine Corps
10 Year Member
Liked
Top Answer: 1
Joined: Dec 2012
Posts: 6,673
Likes: 502
From: Orange County
Default

Originally Posted by Mr.Softy
what octane and gas do you use?
The highest I can get here is 91.
 
Reply
Old May 13, 2017 | 08:37 PM
  #4  
Sling Blade 14's Avatar
Sling Blade 14
Extreme HDF Member
Joined: May 2010
Posts: 11,166
Likes: 1,801
From: Puget Sound, WA.
Default

How's your riding conditions?
Looks like a lot of stop and go build up.
It's never one thing-usually a combo of conditions.
https://www.hdforums.com/forum/touri...f-pistons.html
https://www.hdforums.com/forum/engin...cope-pics.html
 

Last edited by Sling Blade 14; May 13, 2017 at 08:43 PM.
Reply
Old May 13, 2017 | 09:39 PM
  #5  
kngpn's Avatar
kngpn
Seasoned HDF Member
10 Year Member
Liked
Loved
Community Favorite
Joined: Aug 2014
Posts: 10,562
Likes: 5,149
From: Robbm sucks
Default

Is your crankcase venting in to the AC or externally?
 

Last edited by kngpn; May 13, 2017 at 09:43 PM.
Reply
Old May 13, 2017 | 10:39 PM
  #6  
Tommy C's Avatar
Tommy C
Seasoned HDF Member
10 Year Member
Joined: Oct 2015
Posts: 13,542
Likes: 34,779
From: Pine Flat Dam/South Bay Area, CA
Default

Originally Posted by kngpn
Is your crankcase venting in to the AC or externally?
^This^
 
Reply
Old May 13, 2017 | 11:16 PM
  #7  
Road Star's Avatar
Road Star
Thread Starter
|
Seasoned HDF Member
Veteran: Marine Corps
10 Year Member
Liked
Top Answer: 1
Joined: Dec 2012
Posts: 6,673
Likes: 502
From: Orange County
Default

Originally Posted by kngpn
Is your crankcase venting in to the AC or externally?
Originally Posted by Tommy C
^This^
To the air cleaner. I need to mod it so it will vent to the ground.
 
Reply
Old May 13, 2017 | 11:39 PM
  #8  
lh4x4's Avatar
lh4x4
Extreme HDF Member
Joined: Dec 2007
Posts: 13,402
Likes: 941
From: Illinois
Default

That carbon build up has only a minor connection to octane. The higher the octane the slower the burn. The slower the burn the less of the intake charge is burned during the combustion cycle. So high octane has more deposits than the more complete burning lower octane. A fact of life that few folks know or understand.

It is primarily carbon mist build up from the oil mist taken into the intake from the routing of crankcase blow by.

Old school shade tree mechanic method of removal is to remove the air cleaner, run the engine at about 2K rpm and mist in water for awhile. The carbon with absorb the water and loosen. However do not listen to those that say after you do that go run the engine hard to blow out the carbon from the engine. What those folks don't know is that creates extremely higher combustion temps and will rapidly re harden the carbon. Go on mild runs and it will expel the loosened carbon. A good idea is to repeat about every 3K.

New school is to treat the gas with Chevron's Techron additive.

Or just do a mod to expel blow by into a catch can.
 
Reply
HD Forum Stories

The Best of Harley-Davidson for Lifelong Riders

story-0

Harley-Davidson Fat Boy Becomes a Dark, Decepticon-Inspired Custom

 Verdad Gallardo
story-1

6 Weirdest Harley-Davidsons Ever Sold to the Public

 Verdad Gallardo
story-2

7 Times Harley-Davidson Chucked Tradition Out the Window

 Verdad Gallardo
story-3

7 Surprising Harley-Davidson Products that Are Not Motorcycles

 Verdad Gallardo
story-4

8 Best Harley-Davidson Motorcycles Ever

 Pouria Savadkouei
story-5

10 Worst Harley-Davidson Motorcycles Ever

 Pouria Savadkouei
story-6

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

 Verdad Gallardo
story-7

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

 Verdad Gallardo
story-8

Harley-Davidson Reveals Super Cool Cafe Racer Concept

 Verdad Gallardo
story-9

Engraved Rebellion: Inside Bundnerbike's Glam Rock II

 Verdad Gallardo
Old May 13, 2017 | 11:42 PM
  #9  
heritageblue2013's Avatar
heritageblue2013
Grand HDF Member
Joined: Mar 2013
Posts: 4,922
Likes: 589
From: Running with the gators
Default

I run a little av-gas through mine just before an oil change
 
Reply
Old May 14, 2017 | 03:10 AM
  #10  
LoneWoolf's Avatar
LoneWoolf
Stellar HDF Member
Joined: Nov 2015
Posts: 2,726
Likes: 717
From: Pennsyleffinvania
Default

Couple of questions so I can better understand.

1. Does oil level play a role in build-up? Could over filling your oil reservoir, or not keeping it at mid-way on the dip stick play a significant role?

2. How about hard acceleration, good or bad as far as build up?

3. How about lugging the engine, does that have an effect?

On my new Iron, at 500 miles, I pulled the air cleaner off and I would say that there was maybe one drop of oil on the inside of chamber where the breather bolts enter the a/c housing. None on the filter medium itself, and the inside of the housing and cover were dry.
 
Reply



All times are GMT -5. The time now is 03:17 PM.

story-0
Harley-Davidson Fat Boy Becomes a Dark, Decepticon-Inspired Custom

Slideshow: Killer Custom's latest build relies on styling changes rather than performance upgrades, giving the cruiser an entirely different personality.

By Verdad Gallardo | 2026-06-03 18:28:05


VIEW MORE
story-1
6 Weirdest Harley-Davidsons Ever Sold to the Public

Slideshow: From military-inspired singles to scooters and three-wheel utility vehicles, these Harleys took the company far outside its comfort zone.

By Verdad Gallardo | 2026-06-02 18:34:10


VIEW MORE
story-2
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-3
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-4
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-5
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-6
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-7
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-8
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-9
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