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post #1 of 12 (permalink) Old 05-29-2010, 10:10 PM Thread Starter
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pressure in gas tank, bike cuts off

just recently bought a used nighthawk 250 used so i was taking a chance, guess the seller go the best of me. here's my problem, when riding down the road anywhere from 2 - 10 minutes the bike will cut off (warmer days this happens sooner). if i open up the gas cap it pops open and pressure is release that has built up. if i ride with the gas cap open i have no problems. also when i let the bike sit with gas cap on you can hear the tank hissing as pressure is building especially on a hot day, once again when i open up the gas tank pressure is release. also if it sits like this gas starts leaking out of the fuel shut off valve due to the pressure build up. sent it in to local honda dealership, they cleaned out the carbs but that didnt solve my issue. any suggestions???
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post #2 of 12 (permalink) Old 05-29-2010, 11:05 PM
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Originally Posted by teedubb View Post
just recently bought a used nighthawk 250 used so i was taking a chance, guess the seller go the best of me. here's my problem, when riding down the road anywhere from 2 - 10 minutes the bike will cut off (warmer days this happens sooner). if i open up the gas cap it pops open and pressure is release that has built up. if i ride with the gas cap open i have no problems. also when i let the bike sit with gas cap on you can hear the tank hissing as pressure is building especially on a hot day, once again when i open up the gas tank pressure is release. also if it sits like this gas starts leaking out of the fuel shut off valve due to the pressure build up. sent it in to local honda dealership, they cleaned out the carbs but that didnt solve my issue. any suggestions???
Clean or replace your gas cap. It's not venting properly.
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post #3 of 12 (permalink) Old 05-29-2010, 11:49 PM
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Temporary fix: open up the cap a bit when you ride.
Permanent fix: Follow this process.

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post #4 of 12 (permalink) Old 05-30-2010, 08:36 PM Thread Starter
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are all gas caps suppose to allow the tank to breathe / vent. when i take a look at my gas cap there is a rubber gasket where the cap meets the tank like it's intentionally trying to prevent the tank from releasing pressure or taking in air.
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post #5 of 12 (permalink) Old 05-31-2010, 02:02 AM
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that gasket is to prevent leaks, the vent is inside of the cap...there should be some small holes in the middle....check this site out, it's for Kawasaki's, but the principal is the same

http://www.kawasakimotorcycle.org/fo...-stalling.html

scroll down a little and there is a pic of a cap open.....

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post #6 of 12 (permalink) Old 05-31-2010, 11:38 AM
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California models have sealed caps, but there's a vent in the tank to a vapor recovery system. The rest are vented through the cap.

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post #7 of 12 (permalink) Old 05-31-2010, 11:13 PM Thread Starter
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i appreciate the input, i'll try replacing my gas cap and see if that fixes the problem. i hope it does because having the gas cap open is not such a good idea because of fuel spilling out when i turn and when it rains. for my nighthawk i dont see much that i can "clean" to fix the problem so i'll simply replace. thanks for all the advice.
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post #8 of 12 (permalink) Old 05-31-2010, 11:59 PM
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It could be that the PO replaced the seal on the cap, and the new seal is covering the vent. Or, the cap was replaced with a Cali model cap, which doesn't have a vent. On the Suzuki Intruder line, this isn't possible, but you never know.

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post #9 of 12 (permalink) Old 06-01-2010, 02:53 PM Thread Starter
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UPDATE

called the honda dealership to order the cap and they say the 99 nighthawk 250 vents through a tube in the tank not the cap. i havent been home to inspect this but i guess that's where i'll start next. any ideas on what i should look for?
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post #10 of 12 (permalink) Old 06-01-2010, 03:16 PM
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Cannot say for sure on your bike, but on mine it's on the underside of the tank. Probably need to drain and pull the tank for best access.
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post #11 of 12 (permalink) Old 06-01-2010, 03:23 PM
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It's the same on the Cali models of the Intruder 800. Sounds like you need to check that the vent hose isn't squashed by the tank, and the canister isn't plugged.

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post #12 of 12 (permalink) Old 06-01-2010, 04:46 PM Thread Starter
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thanks for the pics, i'll take a look at my bike and report back. i havent seen too many people report this as an issue so i hope to figure it out. thanks for all the help.
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