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I have a problem with my America 800 it's running lean on the right cylinder and when I adjust the mixture screw it makes no difference. The mixture was checked using an AFR meter. The rubbers between the carbs and manifolds have been replaced today still running lean on right cylinder.

The bike sat for 4 years and when I brought it out to get it going again I found the carburetors full of gunk and it would not run so the carburetors were pulled down and cleaned, and while they were apart I put bigger main jets in and blocked the air recycle system.

Someone has told me that the coil is faulty on the side that is running lean but that doesn't make sense. I have check there are no air leaks.

Could it be the idle mixture circuit ?

DucatiKiller
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Dave Anderson
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1 Answers1

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You might have a tear in your CV carburetor diaphragm

At the tops of your carburetors there is a cover with 4 screws that gives access to your CV diaphragm and slide.

The CV (constant velocity) carbs adjust for barometric pressure automatically. The difference in pressure from your intake tract and the atmosphere raises and lowers you slide that has the jet needle in it which meters fuel from you main jet.

An unmetered air issue can cause all of the symptoms you are describing and if you have inspected and tested all of the other areas of the carb between the throttle butterfly and the head perhaps this is the area that is giving you issues.

A tear in the diaphragm would cause what you are illiterating.

here is an image of a slide, jet needle and diaphragm

enter image description here

Inspect the Diaphragm

Pull on it a bit, put your finger behind an area and stretch it across you other finger and look for holes and cracks. Also, ensure that when you put it in the carb you put the ring around the outer edge back in it's groove properly in the top of the carb body. It's very easy to pinch it and damage in when you put the tops back on it. You will want to press the cover on and feel that the diaphragm is proper inside the carb body groove before you screw it down.

DucatiKiller
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