Petcock issue?

[Doc809]

We rode the Iron Butt in Texas this weekend.  My son's 03 std ran out of gas.  Switched to reserve and it was gone too.  Had a gas can on board so we weren't stranded on the side of the road but he averaged 15 mpg for the entire 1047 miles.  We had to stop every 60 miles for 4 gallons of gas.  No smoke. No leaks. But no mileage or power at higher speeds.  Is it the petcock failing or do we need to look elsewhere.  Thanks for any input. Larry

[Daniel Meyer]

Could be the petcock...check it with a mity vac or such.

If it's leaking vacuum, not only do you have a massive vacuum leak, but it won't open fully. This results in starving the front cylinders for gas...and at higher throttle settings...dumping it down the back ones to compensate.

[Chrisj CMA]

First the petcock......the OEM one is a piece of junk IMHO if its not really clicked on good (you feel the ball snap in) then its "ON RESERVE"  It can happen to any of them if youre not careful

Second the mileage...that sounds way too low for a simple thing, but Id check for a big vacuum leak, air cleaner, tire pressure, intake clamps (upper and lower)

Thats a start

[Ricky-D]

Larry, the issues with the petcock are pretty universal and the recommended fixes are many also. Myself, I now have a Pingle.

The mpg on that long a trip is clearly a problem and needs to be addressed.  15 mpg is totally unacceptable for the Valkyrie.

The suggestions for possible causes are cogent and should be considered however one thing that should be done is to "Index the Throttle".

Unless the throttle setting is known while normally riding on the highway you can not formulate an accurate and reasonable response for such a problem as 15 mpg.

You have not mentioned if any work has been performed on the carburetors or the air induction system.

A terribly dirty air cleaner can cause poor mpg as well as a blocked air supply.

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[fstsix]

Well hope somebody is listening  When the Diaphragm splits in the fuel valve the fuel will transfer to the vacuum side of the chamber.Now the first thing is' it will suck fuel into your vacuum line and into to your motor ( gas millage problem ) # 2  When the diaphragm splits it will not allow the stop valve to disengage meaning nothing( no reserve)( no on) it needs Vacuum to open valve. Again i have gutted my valve 5 years ago and Supercharged i like the stock chrome on off look and trouble free  That vacuum deal is as worthless as My DPF filter on my 6.7 Cummins. Good luck