gas tank over flow
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Road Warrior
Joined: Sep 2006
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From: nj
gas tank over flow
I put a different sportster tank on my bike I did notice that the other tank over flow was pinched together. Now on my new tank I purchased I believe is a 95 or 96 has the over flow and according to the parts book has some type of back flow in line with the over flow hose. My question is can I just run the overflow down the frame towards the ground or should I purchase this valve . I do have a vented gas cap . I did notice on my old tank that after running for a long time in the heat I did hear air coming from the gas cap. Is this because that the old vent was plugged and was being vented through the gas cap Thanks
I think that the fuel tanks do not have an overflow line. The newer tanks do however have a vent line, in which case they do not need a vented cap - as long as the vent line is functioning. This line can be run anywhere that is convenient. I have this vague recollection that on my 1998 that i had some years ago it ran into the frame?
On the old tank the vent line was pinched so not working. What happens is that as the engine heats up the heat expands the fuel and air in the tank; as the pressure builds up the air hisses out wherever it can. This pressure buildup is very bad for the carb - it can impede fuel flow and wreck the float.
A related issue has to do with new replacement gas caps. In my limited experience they let air into the tank as the fuel level drops, but do not let air out as it expands from heat, so you get the pressure buildup in the tank. Old OEM gas caps do not seem to do this. It can be cured by drilling a very small hole, say 1/16", in the blue plastic thingy inside the gas cap - then do not overfill the tank.
On the old tank the vent line was pinched so not working. What happens is that as the engine heats up the heat expands the fuel and air in the tank; as the pressure builds up the air hisses out wherever it can. This pressure buildup is very bad for the carb - it can impede fuel flow and wreck the float.
A related issue has to do with new replacement gas caps. In my limited experience they let air into the tank as the fuel level drops, but do not let air out as it expands from heat, so you get the pressure buildup in the tank. Old OEM gas caps do not seem to do this. It can be cured by drilling a very small hole, say 1/16", in the blue plastic thingy inside the gas cap - then do not overfill the tank.
Thread Starter
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Road Warrior
Joined: Sep 2006
Posts: 1,605
Likes: 82
From: nj
Thanks Iron, I thought the overflow is the vent because that I checked that metal tube inside the tank and she goes to the bottom of the outside of the tank. The problem I am having on my bike is that after she starts when she warmed up she sounds like she wants to stall then after a couple of minutes she is okay. The bike ran fine before I changed tanks for when I repainted her. The cap has a vent on it
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