carb problems
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Novice
Joined: Mar 2018
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From: Texas
carb problems
alright, so im a newb to working on harley engines.. with that said, ill jump right in.
im working on a 1992? sportster which i believe is what they call an ironhead engine, (vtwin ofc) with an s&s shorty carb,, well heres the thing, i cannot figure out if its supposed to have a pressurized gas tank like the other bike im working on, its a 1980 ironhead with the same carb, it has a fuel line coming off the back of the generator? (the round thing at the bottom front of the engine) that fuel line hooks into the tank to pressurize it to force fuel into the carb? well on the 1992 i cannot find a line that goes to the fuel tank, i can however find a lil hose fitting right behind where the breather cover goes its coming off the top of one of the heads is that the fuel pressure line by chance?.. or just a vent of some type?? i guess in short all i need to know is if all these bikes with the s&s shorty carb have pressurized fuel tanks. thanks in advance.
im working on a 1992? sportster which i believe is what they call an ironhead engine, (vtwin ofc) with an s&s shorty carb,, well heres the thing, i cannot figure out if its supposed to have a pressurized gas tank like the other bike im working on, its a 1980 ironhead with the same carb, it has a fuel line coming off the back of the generator? (the round thing at the bottom front of the engine) that fuel line hooks into the tank to pressurize it to force fuel into the carb? well on the 1992 i cannot find a line that goes to the fuel tank, i can however find a lil hose fitting right behind where the breather cover goes its coming off the top of one of the heads is that the fuel pressure line by chance?.. or just a vent of some type?? i guess in short all i need to know is if all these bikes with the s&s shorty carb have pressurized fuel tanks. thanks in advance.
Cruiser
Joined: Nov 2015
Posts: 165
Likes: 14
From: rockford
A 92 Sportster has a EVO engine and CV carb. Fuel tank isn't pressurized and relies on gravity for feeding. What you are seeing for hose to air filter is nothing more than a breather line (PCV) to get rid of unburned gases in crankcase. I am guessing you are having a fuel delivery problem, like no fuel? On a 92 there should be a vacuum line that hooks up to the petcock which activates a diaphragm. This diaphragm can go bad and not allow any fuel to get to the carb.
If you have S&S carb someone changed it but still should get fuel. Take a vacuum pump and hook up to diaphragm and see when you apply vacuum if you have fuel flow if not diaphragm is bad or petcock.
If you have S&S carb someone changed it but still should get fuel. Take a vacuum pump and hook up to diaphragm and see when you apply vacuum if you have fuel flow if not diaphragm is bad or petcock.
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Novice
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From: Texas
didnt think this post ever made it up... sorry for the double posting guys... anyway..
norman, thanks for the reply, but you just lost me so bad lol... i need laymens terms lol...
but i guess in short youre saying this bike does not have a line that goes to fuel tank for pressure, so theres got to be something wrong with my carb. ok then... ill swap the whole thing out for the one i know works and see how that goes
norman, thanks for the reply, but you just lost me so bad lol... i need laymens terms lol...
but i guess in short youre saying this bike does not have a line that goes to fuel tank for pressure, so theres got to be something wrong with my carb. ok then... ill swap the whole thing out for the one i know works and see how that goes
A 92 Sportster has a EVO engine and CV carb. Fuel tank isn't pressurized and relies on gravity for feeding. What you are seeing for hose to air filter is nothing more than a breather line (PCV) to get rid of unburned gases in crankcase. I am guessing you are having a fuel delivery problem, like no fuel? On a 92 there should be a vacuum line that hooks up to the petcock which activates a diaphragm. This diaphragm can go bad and not allow any fuel to get to the carb.
If you have S&S carb someone changed it but still should get fuel. Take a vacuum pump and hook up to diaphragm and see when you apply vacuum if you have fuel flow if not diaphragm is bad or petcock.
If you have S&S carb someone changed it but still should get fuel. Take a vacuum pump and hook up to diaphragm and see when you apply vacuum if you have fuel flow if not diaphragm is bad or petcock.
petcock
Last edited by Oddman; Mar 29, 2018 at 11:35 AM. Reason: insert pic
Cruiser
Joined: Nov 2015
Posts: 165
Likes: 14
From: rockford
ok first simple thing. Does carb get fuel to it or it only runs when you spray starter fluid?
Check fuel line from petcock. disconnect it at petcock and turn on. With factory petcock there will be a vaccum line attached to it or should be. If no vacuum line and you see a nipple on back of petcock get a vacuum pump from any auto parts store and see if it holds vacuum. because Harley petcocks from 1988 on are vacuum operated if that doesn't work no fuel
Check fuel line from petcock. disconnect it at petcock and turn on. With factory petcock there will be a vaccum line attached to it or should be. If no vacuum line and you see a nipple on back of petcock get a vacuum pump from any auto parts store and see if it holds vacuum. because Harley petcocks from 1988 on are vacuum operated if that doesn't work no fuel
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Novice
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From: Texas
oh yea for sure, the valve is fine, so is the float,, and i made sure the jets arent clogged,,, and that lil rubber ring thing that sits under or above the spring over to the side of the bowl,,, i replaced that one thing too lol... yea ive never messed with one of these carbs,, but i have a 2 stroke dirtbike that ive had to do alot of carb work to.. so its not completely new to me.. its really just this engine that has me confused
HDF Community Team
Joined: Dec 2011
Posts: 8,550
Likes: 3,975
From: San Diego, CA
No motorcycle fuel tanks are "pressurized." On the EFI bikes, the fuel pump pressurizes the fuel lines to the injectors, that's it. On carburetor bikes, it's all gravity flow.
The "lil rubber ring thing" actually has a name too. It's called the accelerator pump diaphragm. See how easy that is?
Now, a "vented" versus "non vented" fuel tank is a different story. You need to get a basic understanding of how this all works before you can ask good questions. It's hard to help someone when they just use words like thingy, doodad, gizmo, etc.
Words are powerful weapons, choose them carefully.
John
The "lil rubber ring thing" actually has a name too. It's called the accelerator pump diaphragm. See how easy that is?
Now, a "vented" versus "non vented" fuel tank is a different story. You need to get a basic understanding of how this all works before you can ask good questions. It's hard to help someone when they just use words like thingy, doodad, gizmo, etc.
Words are powerful weapons, choose them carefully.
John
Last edited by John Harper; Mar 29, 2018 at 11:58 AM.
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From: Texas
but no, theres not a vaccuum line on it, its just a straight line off the side of the valve that runs directly to the carb,, if i open the bolt on the bottom of the bowl it has fuel in it,,, and also, this may be key to the solution, but when i start it on starter fluid, cause thats the only way it will start) it will continue running at a high rpm if im laying on the throttle,, and i can see the fuel spraying in from the bowl,,, but when i let off it dies.
which is why i was thinking maybe i was missing pressure on the tank or something,, since with the 1980 it does have a line for that exact thing, right?
which is why i was thinking maybe i was missing pressure on the tank or something,, since with the 1980 it does have a line for that exact thing, right?
Last edited by blue-42; Mar 29, 2018 at 11:59 AM.
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Thread Starter
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Novice
Joined: Mar 2018
Posts: 16
Likes: 1
From: Texas
No motorcycle fuel tanks are "pressurized." On the EFI bikes, the fuel pump pressurizes the fuel lines to the injectors, that's it. On carburetor bikes, it's all gravity flow.
The "lil rubber ring thing" actually has a name too. It's called the accelerator pump diaphragm. See how easy that is?
Now, a "vented" versus "non vented" fuel tank is a different story. You need to get a basic understanding of how this all works before you can ask good questions. It's hard to help someone when they just use words like thingy, doodad, gizmo, etc.
Words are powerful weapons, choose them carefully.
John
The "lil rubber ring thing" actually has a name too. It's called the accelerator pump diaphragm. See how easy that is?
Now, a "vented" versus "non vented" fuel tank is a different story. You need to get a basic understanding of how this all works before you can ask good questions. It's hard to help someone when they just use words like thingy, doodad, gizmo, etc.
Words are powerful weapons, choose them carefully.
John
HDF Community Team
Joined: Dec 2011
Posts: 8,550
Likes: 3,975
From: San Diego, CA
It sounds like your pilot jet or idle mixture screw are clogged and you need to clean out the passages with some carb cleaner and reassemble. Carb mix screw should be set at 2.5 turns out from gently seated.
Again, there is NO PRESSURE applied to the fuel tank on any Harley ever made. If anything, it is a vent line for gasoline vapors.
John