Carb leaking, stumped
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Cruiser
Joined: Aug 2012
Posts: 172
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From: Keno
Carb leaking, stumped
I'm working on a friend's sportster. The carb has been leaking fuel.
It's a a 1990 CV carb, on a 1996 XL1200. I'm basing this off the fact that it has the two circular floats used in 88-90 instead of the common U shaped float. Local dealer confirmed this via parts manual. He bought it used a couple months ago.
The floats are intact, and when tested do float. I replaced the float needle, no change. The floats are adjusted properly to HD factory specs. The drain screw o ring is good, the bowl will hold fuel and not leak from there when testing. Accelator pump o ring is new. The jets are clean, the bike runs great aside from this issue.
I just dissasembled the entire carb, and I think the diaphram may be degrading. There was a thin layer of black sooty-looking stuff all over the inside of the carb, even in the upper end. It was everywhere. Not brown, gummy carb looking crap, it was jet black and a very fine layer. I've never seen a carb dirty like this on the upper end. The bowl was clean.
What am I missing? I'm assuming at this point that a vent passageway somewhere is clogged.
-- The petcock does leak slightly, and I'm going to rebuild it, but regardless - the float needle should still stop the flow of fuel.
I'm stumped.
It's a a 1990 CV carb, on a 1996 XL1200. I'm basing this off the fact that it has the two circular floats used in 88-90 instead of the common U shaped float. Local dealer confirmed this via parts manual. He bought it used a couple months ago.
The floats are intact, and when tested do float. I replaced the float needle, no change. The floats are adjusted properly to HD factory specs. The drain screw o ring is good, the bowl will hold fuel and not leak from there when testing. Accelator pump o ring is new. The jets are clean, the bike runs great aside from this issue.
I just dissasembled the entire carb, and I think the diaphram may be degrading. There was a thin layer of black sooty-looking stuff all over the inside of the carb, even in the upper end. It was everywhere. Not brown, gummy carb looking crap, it was jet black and a very fine layer. I've never seen a carb dirty like this on the upper end. The bowl was clean.
What am I missing? I'm assuming at this point that a vent passageway somewhere is clogged.
-- The petcock does leak slightly, and I'm going to rebuild it, but regardless - the float needle should still stop the flow of fuel.
I'm stumped.
HDF Community Team
Joined: Dec 2011
Posts: 8,598
Likes: 4,028
From: San Diego, CA
I left my petcock on one time, and it opened the float needle valve, could have been related to a full tank of gas. Except for that, it never leaks. I'd just rebuid the whole enchilada and get a fresh take. Fix the petcock leak too.
John
John
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Cruiser
Joined: Aug 2012
Posts: 172
Likes: 0
From: Keno
Not the cables, it'll do it when only the fuel hose is attatched to the carb for testing. I have found that the float height setting on this thing is crazy sensistive.
At 15 degrees, like the manual specifies, I had it set to .710. Fuel was pouring out. I set it to .730, and it was so starved the accel pump would only get one good suirt before it starved.
It's a .720 now, and the leak is still there, but it's very slow. I'm wondering if ethanol in the fuel has degraded the floats and now they're not acting right?
At 15 degrees, like the manual specifies, I had it set to .710. Fuel was pouring out. I set it to .730, and it was so starved the accel pump would only get one good suirt before it starved.
It's a .720 now, and the leak is still there, but it's very slow. I'm wondering if ethanol in the fuel has degraded the floats and now they're not acting right?
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