EVO All Evo Model Discussion

Compliance fitting

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Old Aug 31, 2012 | 02:53 PM
  #11  
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Originally Posted by notlost_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.
I still have a set on my part shelf I had for my 1989 Ultra.
I never used them because I replaced the manifold with an S&S Solid Manifold.
 
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Old Aug 31, 2012 | 04:57 PM
  #12  
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Originally Posted by Scratt
The older EVO's used rubber hose's (radiator hose) from the intake manifold to the heads.
Those rubber parts are compliance fittings.

The compliance fittings and the butterfly Keihin carbs made their last appearance on the `89 model year bikes.

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?
The old type butterfly carb that you currently have is a very reliable carb, but is a dog as far as performance goes...

To upgrade to a later model carb configuration, you would need to find :

CV carb (made for a Harley)

Intake manifold, Backing plate, Air filter and Air filter cover (`90 or later carb model bike).

These parts are easily found on the well known online auction site.

There are also aftermarket carburetors, the S&S E model, and the Mikuni HSR 42, however, they would cost much more than buying used parts to upgrade to the CV carb.
 

Last edited by Dan89FLSTC; Aug 31, 2012 at 05:00 PM.
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Old Aug 31, 2012 | 04:58 PM
  #13  
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Seeing as I am the FNG around here... What does the CV in "CV carb" mean?
 
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Old Aug 31, 2012 | 06:36 PM
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I believe it means constant velocity.
 
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Old Aug 31, 2012 | 06:53 PM
  #15  
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By the way, glad it worked out for you!

I've never heard of the rubber hoses being called compliance fittings, only the gasket. Thanks for the heads up Dan.
 
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Old Aug 31, 2012 | 07:29 PM
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Originally Posted by Jim Kraft
I believe it means constant velocity.
Good reminder of how much I have left to learn about these mighty steeds. Not a clue what that means.
 
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Old Aug 31, 2012 | 08:54 PM
  #17  
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Originally Posted by FlyBD5
Good reminder of how much I have left to learn about these mighty steeds. Not a clue what that means.
Means that no matter what throttle position is the air flow velocity through the carb is constant. Makes it easier to more precisely mix fuel by taking out a variable, and allows the carb to efficiently operate over a much wider range of altitudes. The butterfly-type carb's air flow velocity changes with throttle position.
 
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Old Aug 31, 2012 | 08:59 PM
  #18  
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Originally Posted by pococj
Means that no matter what throttle position is the air flow velocity through the carb is constant. Makes it easier to more precisely mix fuel by taking out a variable, and allows the carb to efficiently operate over a much wider range of altitudes. The butterfly-type carb's air flow velocity changes with throttle position.
That made perfect sense! Thank you. Yet another item for the winter project checklist.
 
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Old Sep 4, 2012 | 08:11 AM
  #19  
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Originally Posted by FlyBD5
Yet another item for the winter project checklist.
As I mentioned above, that was the first mod I made to my '89 when I first got it. I got a used CV, along with a new manifold/air filter kit and it made all the difference in the world. I have since swapped out that old CV for a Wood-built CV, but that old used carb with a little TLC served me well for five years.
 
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Old Sep 4, 2012 | 10:43 AM
  #20  
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Yeah, the compliance fittings were A Bad Idea. I would have to replace them about once a year, two on the outside. I now have the S&S solid manifold and have not had an intake leak since. Knock on wood.
 
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