Fuel Supply Question

[grumpyone]

Ok this may be way off the wall but just got to thinking about it.
We have a cross over on our fuel line connecting both. If you turn on the right fuel petcock and then it runs out , turn on the left side the right side is to be left on? or turned off ? when you switch to the left side. If you leave it on will it create a air lock or suck air or? Also same case when you get to the reserve on the right when it runs out and your on your left reserve should the petcock on the right be turned off whenever you are below its pickups and you turn on the left side? Or would it not make any difference.
Just a passing thought?
Jim and Esther

[PineGreen]

No problems should be encountered no matter which petcock you have turned on or off, and for that matter sequence doesn't matter either.. Some cut the reserve tube, on one or both petcocks, shorter thus hoping to suck more fuel out. There may be some nasty stuff lurking in the bottom of your tank though.. Never been brave enough for that one

[swall]

Both petcocks have a standpipe for the main fuel and when the level drops below the standpipe, you switch to reserve, which picks up the rest of the fuel below the standpipe intake. From here on it is personal preference--you can switch both petcocks to run and then switch both to reserve when you start sputtering. Or, you can run one petcock in main and leave the other off and when the first runs out, you switch to the second main until you hit reserve again. No problems either way, except eventually running out of fuel with either scheme.

[20774]

There's no airlock created no matter which way you switch things. The tank is (or at least should be) vented. The side that has run "dry" has air above it from the vented gas tank. No matter...the gas on the other side of the tank is being forced via gravity to run across and down to the opposite carb. I suppose if it were running fast enough, it might create a venturi effect as is passed the empty fuel line down from the "dry" side of the tank...but that's certainly not going to happen.

[RickyT]

I have run out of fuel twice now because my reserve doesn't work. The first time I attributed it to the rust and other gunk that was clogging the petcock/fuel filter. After cleaning the tank, replacing the filters, replacing the fuel lines, etc I ran out again and when I switched to reserve no fuel was left in the tank. I checked the petcock tubes and valve and the reserve does flow from the shorter tube. Does anyone know why I can't rely on the reserve? Oh yeah- it's an 85 R80.

[AnnapolisAirhead]

I have run out of fuel twice now because my reserve doesn't work. The first time I attributed it to the rust and other gunk that was clogging the petcock/fuel filter. After cleaning the tank, replacing the filters, replacing the fuel lines, etc I ran out again and when I switched to reserve no fuel was left in the tank. I checked the petcock tubes and valve and the reserve does flow from the shorter tube. Does anyone know why I can't rely on the reserve? Oh yeah- it's an 85 R80.

This might sound obvious, but are you sure you aren't riding on reserve, thinking its actually the 'on' position? What kind of petcocks do you have? I have Karcomas, straight nipple. Off is level with the horizon (9:00 or 3:00), lever pushed down (e.g. 6:00) is the 'on' or normal position. Up (noon) is the reserve position.

If not that, have you cleaned you tank? Seems odd.

[RickyT]

That makes sense. It's so befuddling to me that the solution must be obvious. I'm setting the switch such that the long end of the handle points 12:00 and the short pointy end at 6:00. I think I will take the petcock off and test the reserve vs main switch position. Thanks!
Rick

[mneblett]

That makes sense. It's so befuddling to me that the solution must be obvious. I'm setting the switch such that the long end of the handle points 12:00 and the short pointy end at 6:00. I think I will take the petcock off and test the reserve vs main switch position. Thanks!
RickNo need to take the petcock off -- I've had a number of airheads since the '70s, and they were *all* long-part-of-the-lever down for main, long part up for reserve.

HTH!

[RickyT]

Well that is the problem- I've been riding on reserve. I love simple solutuions! Thanks. Can you tell I've only had it a few weeks and it's my first bike???

[AnnapolisAirhead]

Well that is the problem- I've been riding on reserve. I love simple solutuions! Thanks. Can you tell I've only had it a few weeks and it's my first bike???

No worries, we are all new to airheads sooner or later. I had he same befuddlement with my first airhead just a few months ago. Just remember if the lever is in the 'up' (that is, 12:00 position) it's time to 'fill her UP' because you are on reserve.

Conversely, if the lever is 'down' (that is, the 6:00 position) its time to ride on DOWN the road.

Anything else (9:00 or 3:00) the fuel is shut off.

Happy riding. :dance