Gas tank cap vent

Art Lischer alisch80 at
Mon Jul 2 18:10:19 PDT 2007

Had similar happen in E CO on way to Fandango.  Try fiddling with the 
vacuum line to the petcock. It might be kinked causing petcock to shut 
off fuel supply when in "ON" position.  

Also try rearranging the carb bowl vent lines; if the ends of the hoses 
get in a place where there is air or turbulence it won't allow bowls to 
vent and slows gas flow.

Does the cap whistle or whine after sitting a few minutes in the sun?  
If so the cap is venting properly.
HTH,   Art in DM

Larry Zoia wrote:
> Gentlemens,
>   Could someone enlighten me as to a procedure to check whether or not 
> the gas tank cap vent is patent?
>    I suspected a venting issue, so of course I shot some
> WD-40 into the holes and blew them out with compressed air.  When my 
> problem didn't resolve, I
> (belatedly) looked in the manual.  It didn't tell me how
> to check the venting.  It DID tell me not to use compressed air.
>    During long periods of sustained high speeds (80-90 mph from 
> Michigan to NJ this weekend) I noticed symptoms of fuel starvation 
> which were ameliorated
> somewhat by running with the petcock in the Prime position.
>    Coming out of a gas stop, the bike, warm, runs great for about 20 
> minutes at 85 mph or so, and then the starvation symptoms begin.  Same 
> thing when I stop to pay a toll with the petcock in the Prime 
> position.  I tried to look at the glass filter on the fly to check the 
> amount of gas therein, but that manuever seems to result in a soft 
> left turn and horns being honked.
> plan is to check the flow through the inline
> filter (glass) to make sure the filter isn't the issue, then
> remove and inspect the petcock for....well, whatever I
> might find, and then back to square one with the venting.
>   I do have a recently installed Stage III jet kit, but my
> mileage has been around 44 mpg for aggressive highway (turnpike) riding.
>  I remember hearing what I interpreted as air being sucked through the 
> cap vent after idling the bike in the
> garage for a few minutes, and this is what prompted me
> to blow out the holes.
>   Thanks in advance for any responses.
> Larry in Michigan

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