Full Gas Tank problem

[airbornesamurai]

Has anyone heard of this before.

Got my 81 GS400 running finally after replacing the Petcock vacum line and changing out the spark plugs, runs and pulls great. Fill her up full of gas and within 5 minutes she was bogging down at low speed, losing power, stalling and spilling gas on the ground. She would start up again and buck and spit for a minute thentake off again for another little while.

So today I drained most of the gas out of the tank and took her for a run, both on the hiway and around town,40 km later she was running fine???????

Is this a float level problem or somwthing else?

Had the same problem last year but never made the connection to a full tank, casue it would only happen every now and then

Thanks for all and any ideas

Paul

[Krunk_Kracker]

Did you replace the petcock, or just the vacuum line?

[tkent02]

Test the gas tank vent, it's located in the gas cap. The vent is through the keyhole, probably.
If there's no vent, there's no fuel flowing, and it's worse with a full tank.

Test it by cracking the cap open to see if it fixes it.

[airbornesamurai]

Just replaced the line

Would a blocked tank vent cause the gas bukking??

Thanks

Paul

[BassCliff]

Hi,

Would a blocked tank vent cause the gas bukking??

As fuel leaves the tank, air must get in to replace the lost volume. Otherwise a vacuum will be created which will not allow the fuel to flow out of the tank and into the carbs. This is called "fuel starvation" and will cause your engine to burp and fart and eventually die.

The gas cap must vent properly. They can usually be taken apart and cleaned. The filler neck in your fuel tank has a hole for venting purposes. This also must not be blocked.



And most importantly, is your fuel tank clean? Are you carbs clean? Any sediment or debris in your tank may make its way into your carbs and clog up small passages. Is your air filter clean?

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BassCliff


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