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Discussion Starter · #1 ·
I,M got to ask something that is probalbly a stupid question .can a gas cap go bad on a motorcycle??
Before you roll over in the floor laughing at me let me explain.
I have a close friend with an 03 vulcan nomad fi,about a month ago his bike started running terrible,at slow speed the bike would surge continually ,flood real bad and would not idle.
When you first start the bike(cold start) it would run good for a few minutes then the problem would start.
Your can then let the bike set for about three hours and again it would run good for about five minutes.
He took the bike to our local dealership and they told him the bike was just low on antifreeze he brought the bike home(in a trailer because of bad weather)and the first time he tried to ride it he had the same problem.
Yesterday I tried to help him fix his problem I ran the self diagnostic on the bike (thanks to T-Man for telling me how)and came up with nothing.To make a long story short
when you open the gas cap and run and ride the bike it runs perfect when you close the cap the problem will develop in just a few minutes.Also the tank builds up a lot of pressure when you shake bike around ,I tried the same thing on my vulcan and it doesnt do that.
We checked all the vent lines and they are all open.
Has anyone ran across this problem before??
 

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Rebel Rider
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Check the tank vent line, sounds like it is clogged or crimped. Start at the cap, it has to vent through the cap into the line.

bluestringer
 

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Discussion Starter · #3 ·
we,ve checked all the vent lines and the are not clogged
 

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TimR said:
we,ve checked all the vent lines and the are not clogged
If you have done all that it seems to me the vent in the cap itself is not open. Try blowing it out with compressed air. Could be a piece of rust from water condensation in the fuel.
 

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re

there are valves in the cap to let air in as fuel is used as well as hose vents
from the tank,and a little prong on the cap that engages the hose vent
pressure may be building from no air getting in.

try replacing the cap-although i've never seen one go bad that quick
some vulcan caps whistle and there is a fix for it but it involves dis-assembly
of the cap and there are many very small springs and valves in there
PITA!
 

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I think you guys are on the right track with the gas cap.I have an 800B and it did the same thing except worse.I asked the same question on this forum and was told by 2 people to adjust the rubber seal under the gas cap.I t
rotated this rubber gasket a few times before I found the right spot but now it runs great.I tried all the same thing you did too.Now when I shake the bike you can hear the air vent from the cap.Maybe it's the same problem on the 1500?My dealer said he never heard of this.Good Luck.
 

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A friend of mine with a Vstar 1100 had his tank replaced after a previous owner damaged it. Turns out the tank was for a California model, and he ended up having problems with vapor lock because of the sealing. I wonder if this is reversed in your case? Maybe someone has some else insight on it.
 

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Rebel Rider
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vanb said:
I think you guys are on the right track with the gas cap.I have an 800B and it did the same thing except worse.I asked the same question on this forum and was told by 2 people to adjust the rubber seal under the gas cap.I t
rotated this rubber gasket a few times before I found the right spot but now it runs great.I tried all the same thing you did too.Now when I shake the bike you can hear the air vent from the cap.Maybe it's the same problem on the 1500?My dealer said he never heard of this.Good Luck.

Same thing on my 800A. Also there are tiny rubber o-rings under the cap screws, mine were not sealing good. After removing them and replacing, the problem went away.

bluestringer
 
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