Compliance fitting
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Cruiser
Joined: Aug 2012
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Compliance fitting
Hi folks,
I found some threads that talk about this but not enough information to understand what it all means.
Just got my 89 FLHS back from the shop and one of the things they did was replace something called "compliance fittings". I can't find that in the shop manual and I have no clue what they do, other than they seem to have something to do with the intake manifold?
The truth is, my bike runs a LOT better now. I also saw some comments that it's best to throw those away and replace them with something else. Why, and what is the best way to go for replacements?
I'm all ears.
I found some threads that talk about this but not enough information to understand what it all means.
Just got my 89 FLHS back from the shop and one of the things they did was replace something called "compliance fittings". I can't find that in the shop manual and I have no clue what they do, other than they seem to have something to do with the intake manifold?
The truth is, my bike runs a LOT better now. I also saw some comments that it's best to throw those away and replace them with something else. Why, and what is the best way to go for replacements?
I'm all ears.
Thread Starter
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Cruiser
Joined: Aug 2012
Posts: 106
Likes: 0
No sooner posted, I found this. Is this an accurate description of the issue and the solution? Is S&S a good option for this?
The S&S manifold conversion kits for Harley-DavidsonŽ EvolutionŽ big twin engines are designed to replace the original rubber "compliance fitting" style manifold and seals used on 1984-'89 big twins, with a rigid mount aluminum manifold. The stock style rubber compliance fittings, used in this range of model years, are subject to degradation due to heat, age, and exposure to petroleum products. Intake leaks are a common problem with the compliance fittings due to cracks in the rubber.
The most common symptom of an intake leak is an erratic idle, but intake leaks can cause poor overall performance, and in extreme cases, can cause serious engine damage due to a lean mixture in one or both cylinders. By upgrading to the S&S rigid mount manifold, these cracking and leaking problems are eliminated. In addition, the improved flow of the S&S manifold can help improve performance.
The S&S manifold conversion kits for Harley-DavidsonŽ EvolutionŽ big twin engines are designed to replace the original rubber "compliance fitting" style manifold and seals used on 1984-'89 big twins, with a rigid mount aluminum manifold. The stock style rubber compliance fittings, used in this range of model years, are subject to degradation due to heat, age, and exposure to petroleum products. Intake leaks are a common problem with the compliance fittings due to cracks in the rubber.
The most common symptom of an intake leak is an erratic idle, but intake leaks can cause poor overall performance, and in extreme cases, can cause serious engine damage due to a lean mixture in one or both cylinders. By upgrading to the S&S rigid mount manifold, these cracking and leaking problems are eliminated. In addition, the improved flow of the S&S manifold can help improve performance.
Advanced
Joined: Jul 2012
Posts: 51
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From: upstate ny
The compliance fitting is the rubber part of the intake there pretty big they bolt to the heads and the manifold goes into them they crack and tear. sometimes you can't even see the crack but it will suck air under load so they can go undetected. I think they were on early evos till 90 or so
Road Master
Joined: Jun 2007
Posts: 842
Likes: 47
From: New Hartford CT
The first thing I did to my '89 when I got it several years ago was to swap out the old butterfly carb and manifold with compliance fittings for a late model CV carb and manifold. Instant noticeable improvement. I believe '89 was the last year for that carb/manifold type, with good reason.
Road Master
Joined: Sep 2006
Posts: 1,121
Likes: 6
From: Huntersville, NC
The compliance fitting was replaced by an aluminum intake that was rubber mounted to the heads. This allowed a bit of give and take as the head heated up and cooled off. I replaced mine and never had another leak. Are those fittings even available anymore? Should be obsolete....that's one part we can do without.
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Outstanding HDF Member
Joined: Nov 2010
Posts: 2,627
Likes: 3
From: S.E. Va
The older EVO's used rubber hose's (radiator hose) from the intake manifold to the heads. HD then upgraded to solid "Y" with rubber O rings between the intake and the heads. The "compliance" gasket is the rubber gasket (flat O ring with a groove) that get's placed onto the intake manifold (behind the carb) and then the carb is pushed into that.
The solid mount in my opinion works better then the hoses, my Brother has an 86 Wide Glide and he went with an S&S carb (Super E, intake included ). He loves it.
The solid mount in my opinion works better then the hoses, my Brother has an 86 Wide Glide and he went with an S&S carb (Super E, intake included ). He loves it.
Last edited by Scratt; Aug 30, 2012 at 09:41 PM.
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Thread Starter
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Cruiser
Joined: Aug 2012
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Well, the bike runs a heck of a lot smoother with the new compliance fittings. Before it would miss once in a while at cruising speed, and it just wasn't smooth at lower RPM's. It sounds and feels a lot better now.
Seasoned HDF Member
Joined: Jun 2010
Posts: 9,324
Likes: 3,869
From: Upstate New York
As I remember, there used to be a "secret" recall on the old style manifold back in the day. "Secret", in that Harley would cover the cost of replacement if the customer complained, otherwise not. I found out about it by overhearing someone discussing it at the parts counter at the dealership. That's how I got my Sportster upgraded.
Of course, that was long ago. Today, Harley barely acknowledges that they ever built the Evo, let alone warrants anything.
Of course, that was long ago. Today, Harley barely acknowledges that they ever built the Evo, let alone warrants anything.