Both petcocks on?

[georgej]

Do most of you or any of you turn both petcocks on when riding? I looked at some posts on reserve,but exactly how does this tank work? I usually turn the right one on until she sputters then I use the left one until I fuel up.

[crazydrummerdude]

I'm no expert, but.. I ride with both on.

When it sputters, I turn on one reserve.
When it sputters again, I turn on the other and find the nearest gas station.

[Braddog]

Keep both of them on when riding normally. Some ride with one on and one on reserve, then just turn the other on reserve when it starts to sputter. I just keep them the same.

[SoFloPro]

i ride with both on, the only problem i have is i dont think they are working properly, the last few long rides i had, as son as i felt a sputter, i switched them both to reserve, but didnt make it even 5 miles to a gas station..... the petcocks are new... could they have been installed wrong? i used to be able to ride at least 15 miles on reserve no prob before, even more i think, never really measured. anyone...?

[kgadley01]

Do most of you or any of you turn both petcocks on when riding? I looked at some posts on reserve,but exactly how does this tank work? I usually turn the right one on until she sputters then I use the left one until I fuel up.

when I had my Airhead, I rode with both on. once at a dealer they noticed this and explained it like this.....Ride with the left one on and the right one off. if you need to hit reserve turn the left one to reserve. if your reserve runs out. (don't be that stupid) turn your right one to reserve. you've got aprox two miles left in that fuel line. I don't claim any of this to be true, its just what they told me at the BMW dealer!!!!!

[GregFeeler]

i ride with both on, the only problem i have is i dont think they are working properly, the last few long rides i had, as son as i felt a sputter, i switched them both to reserve, but didnt make it even 5 miles to a gas station..... the petcocks are new... could they have been installed wrong? i used to be able to ride at least 15 miles on reserve no prob before, even more i think, never really measured. anyone...?

Sounds like the stand off pipes (or one of them) have fallen out of place. You might be able to eyeball them through the filler cap, but likely you'll need to pull them out for a good inspection. This is not an uncommon problem.

[sumran]

What bike and tank do you have?

I ride with both on. I have gone as far as 40 miles on reserve. I have long straws on my primary setting. If I get gas as soon as I go on reserve, it takes 4.3 gallons to fill it up. The tank capacity is 6.4 (I think). Iam sure some of the gas would be trapped, but most of it should come out in the reserve setting.

Something has to wrong on yours. Perhaps the one of the straws came loose on install.

[GregFeeler]

The airheads are designed to use the gravity pressure of both petcocks turned on. That way you get plenty of fuel flow at higher speeds, and the fuel can equalize it's level between both sides of the tank once the fuel level is below the saddle hump of the frame backbone. Normally, you should have about a half-gallon of fuel on each side once you hit reserve.

IF you decide to run on petcock, I'd recommend doing a flow test to make sure you are getting plenty of flow. Over time the screens over the pickup tubes in the tank can have a crud build up and reduce the flow.

[DarrylRi]

I have an R90S now and previously had an R80, and I've always run both of them with just the left side petcock. There is plenty of fuel flow for both cylinders through one petcock (has to be, or switching to one side's reserve wouldn't be enough to get you down the road).

Also, the advantage to using one petcock is that the fuel hose length to the right cylinder is longer than the left, so when you first run out of fuel, it's only on the left side and you have a few seconds of time to get the reserve switched over before the right side sputters as well. If you have both petcocks on, they will balance the fuel and both cylinders will run dry pretty much simultaneously.

[rocketman]

The airheads are designed to use the gravity pressure of both petcocks turned on. That way you get plenty of fuel flow at higher speeds, and the fuel can equalize it's level between both sides of the tank once the fuel level is below the saddle hump of the frame backbone. Normally, you should have about a half-gallon of fuel on each side once you hit reserve.

IF you decide to run on petcock, I'd recommend doing a flow test to make sure you are getting plenty of flow. Over time the screens over the pickup tubes in the tank can have a crud build up and reduce the flow.

Which is why if you have not cleaned them out to do so. The red lining material in the tanks can flake off over time and crud builds up. Last year when my 78 R100 started giving me problems with sputtering and poor acceleration I drained my tank and removed the petcocks. The screens were really gummed up. After cleaning the tank out as well as the screens the bike has been running smoother than it had in years. Well worth the time (less than an hour).

I too always run with both on, when I have to go to reserve, I flip the left one first which gives me around 20 some miles and then the right at which point I know I have only 20 some miles left and better find gas quickly.

RM

[donbmw]

On my R90/6 I have always run with them on then switch to resvere and go about 40 miles also. On my R65 which only has one petcock it is about the same miles on resevere.

Don

[jforgo]

if I really get on my R100's, a single petcock seems insufficient. Coughing/sputtering.
Also, by usually running only one side, you may be allowing water buildup on the other side.

[535is]

Interesting thread with plenty of perfectly plausible theories. The only one I don't quite buy is that by running both sides at once, they will empty simultaneously. Maybe once in awhile, but I would think the 'slosh factor' would generally preclude that. ;)

I do not have an ingrained habit since all my previous bikes have had only one petcock on the left. On the Airhead, I tried running on one and I found it perfectly satisfactory. I don't run really high speeds and I don't usually rev it too awfully high, so fuel flow is good enough from one petcock. Unlike other 'one open runners', though, when running one until 'below the hump', I use the right one because I can then open the left one without using my throttle hand. This is especially handy in moving traffic where I want the transition done as smoothly and quickly as possible - so I don't get run over. I can then switch the right one to reserve at my leisure and close the left again. When the right goes empty, I use the same move as before, with my left hand opening the left reserve, as I get ready to walk the final miles to the next fuel stop ... :bluduh

I am still open to sincere and logical suggestions, though, as long as they carry with them the strong threat of imminent and permanent damage to my engine. :stick

[The_Veg]

A friend of mine was once running on one petcock and stalled the bike leaned over in a turn, with the 'on' side being the side that was higher in the lean.

I run both.

[535is]

A friend of mine was once running on one petcock and stalled the bike leaned over in a turn, with the 'on' side being the side that was higher in the lean.
Well, that brings up an interesting physics question. Does the fuel in the tank not remain essentially level (with respect to the bike) in a steady state turn? It seems that centripetal force would dictate that it does - and your friend was just the victim of an ill-timed turn, not fuel running downhill due to the turn. Now, I have run short of fuel in my car in Road America's Carousel (more than once - don't ask! :bluduh ), but on a car, the car stays level and the fuel is pushed to the (unfortunately for me, wrong) side of the tank so starvation can occur. But on a bike, the fuel is pushed toward the bottom of the tank in the turn. Not surprisingly, this is the same simple principle that keeps you in your seat (as opposed to falling to the ground) in a hard turn.

So 'splain dat, Loocy! :lurk

[rpeckham136133]

:lurk

My .02:

Some bikes run without the crossover, which requires both to be open (duh!).

However, with the crossover installed, either petcock SHOULD be able to feed the engine, assuming that the crud-screen is clean. That crossover is there so that both carbs get the benefit of fuel, sloshing or not, turning or not. By using only one, you have the benefit of two separate reserves (sloshing notwishtanding)/

Personally, I am with Darryl Richman (who should know!), in that I have a /2 as well, with only one petcock on the left side. I can cross-bike easily as I have been well trained by my /2 to ALWAYS shut off the petcock, so one is easier to do! Plus, the other argument that, when low on fuel, it is easier in traffic to reach down on the left side whilst the right hand stays on the throttle....and the right tank reserve is still there (sloshing?) when it is desperation time!

All boils down to preference, now, doesn't it!

[rocketman]

Interesting thread with plenty of perfectly plausible theories. The only one I don't quite buy is that by running both sides at once, they will empty simultaneously. Maybe once in awhile, but I would think the 'sloshed factor' would generally preclude that. ;)

I do not have an ingrained habit since all my previous bikes have had only one petcock on the left. On the Airhead, I tried running on one and I found it perfectly satisfactory. I don't run really high speeds and I don't usually rev it too awfully high, so fuel flow is good enough from one petcock. Unlike other 'one open runners', though, when running one until 'below the hump', I use the right one because I can then open the left one without using my throttle hand. This is especially handy in moving traffic where I want the transition done as smoothly and quickly as possible - so I don't get run over. I can then switch the right one to reserve at my leisure and close the left again. When the right goes empty, I use the same move as before, with my left hand opening the left reserve, as I get ready to walk the final miles to the next fuel stop ... :bluduh

I am still open to sincere and logical suggestions, though, as long as they carry with them the strong threat of imminent and permanent damage to my engine. :stick

Not a good idea to ride if under the infulance of the "sloshed" factor! :lol

OK, all kidding aside, the balance tube that run between the petcocks (thru the airbox) keeps the level of both side even, even with some sloshing it will quickly balance out again.

RM

[rocketman]

:lurk

My .02:

Some bikes run without the crossover, which requires both to be open (duh!).

However, with the crossover installed, either petcock SHOULD be able to feed the engine, assuming that the crud-screen is clean. That crossover is there so that both carbs get the benefit of fuel, sloshing or not, turning or not. By using only one, you have the benefit of two separate reserves (sloshing notwishtanding)/

Personally, I am with Darryl Richman (who should know!), in that I have a /2 as well, with only one petcock on the left side. I can cross-bike easily as I have been well trained by my /2 to ALWAYS shut off the petcock, so one is easier to do! Plus, the other argument that, when low on fuel, it is easier in traffic to reach down on the left side whilst the right hand stays on the throttle....and the right tank reserve is still there (sloshing?) when it is desperation time!

All boils down to preference, now, doesn't it!

By using only one, you have to go to reserve a lot sooner, I see no advantage since even using both you can still have two reserves, unless you mean you could have three, reserve one being opening up the other side to "on" then reserve two by opening up reserve on one side then three by opening up the other. Guess being able to say you have 150miles of reserve would be impressive, though! :lol
I don't know how much of a time saver that would be either, by only opening one, but hey that one half second saved may be your own, (or something to that effect!) so go for it! :lol

RM

[20774]

Maybe a fourth reserve?? When finally running out of gas with the two petcocks, take the tank off and drain the remnants from one side of the saddle into the other, and reinstall the tank. Now, you really need to find a gas station!!

[9842]

Ride with the left one on and right one off. Fill up before a days ride and don,t worry about running out of fuel. When it sputters put the right side if on, I keep my throttle lock on so the revs go down slowly, so I do not worry about slowing down. Then reserve left and reserve right. I ge about 20 miles to each switch over and have been doing it for 32 years. Once in a great while I will go crazy and start off with the right side just for the fun of it
Later
Brian

[20774]

Once in a great while I will go crazy and start off with the right side just for the fun of it

Probably should consider doing that more often...I know I should! If you constantly only use the left side and it's reserve, the gas that sits at the bottom of the right side, below the reserve straw, gets stale and water collects down there. If you use all part of the gas to a equal degree, you prevent that from happening. It's hard to get to the water that may be collecting at the bottom...some will be run through the engine. But to get at that, you'll need to take the tank off and clean/dry it out from time to time. The water can rust the tank from the inside out.

[GregFeeler]

Interesting thread with plenty of perfectly plausible theories. The only one I don't quite buy is that by running both sides at once, they will empty simultaneously. Maybe once in awhile, but I would think the 'slosh factor' would generally preclude that. ;)

To have the option to use a single petcock both have to be tied together with the crossover tube (stock setup). One of it's main purposes is to act as a balance tube between the two sides of the tank. Once "below the saddle" the fuel will equalize it's level using the crossover tube.

[The_Veg]

Well, that brings up an interesting physics question. Does the fuel in the tank not remain essentially level (with respect to the bike) in a steady state turn? It seems that centripetal force would dictate that it does - and your friend was just the victim of an ill-timed turn, not fuel running downhill due to the turn. Now, I have run short of fuel in my car in Road America's Carousel (more than once - don't ask! :bluduh ), but on a car, the car stays level and the fuel is pushed to the (unfortunately for me, wrong) side of the tank so starvation can occur. But on a bike, the fuel is pushed toward the bottom of the tank in the turn. Not surprisingly, this is the same simple principle that keeps you in your seat (as opposed to falling to the ground) in a hard turn.

So 'splain dat, Loocy! :lurk

He wasn't going very fast- basically was quite low on fuel and making a big-ish left turn into the gast station.

[ducatipaso]

always. i'm a rebel. ;)

[535is]

He wasn't going very fast- basically was quite low on fuel and making a big-ish left turn into the gast station.
I still don't think that makes a difference. Not unless he was steering only with the bike bolt upright (which we all know will crash you right now) - like with a sidehack.

[rpeckham136133]

Fact: a well-flown barrel roll will keep 1G constantly while the plane is one its side, while it is upside down, and on its other side..... Theoretically, that cup of coffee would not spill, even with the plane upside down.

So, the gas should be "pressing" straight down the vertical axis of the bike as it leans into turns (exception is sidecar, as above, but they built special sidecar float chambers on the old BMW's)

How's that for physics, turns, and the state of the universe!

(This is starting to sound like the /2 forums on yahoo)

Bob Peckham
Vero Beach FL
1966 R50/2
1975 R60/6 "project"

[rocketman]

always. i'm a rebel. ;)

http://www.womenwritersblock.com/images/5Rebel.jpg

:lol

RM

[zoridog]

I run both on ... my riding partner uses the "one off" philosophy. Do you know how I found this out?

We were riding back from a rally doing about 75 mph. When his fuel went empty, his bike slowed very quickly. He leaned over to open the other petcock and veered into my lane. Making matters worse, a car was passing us in the left lane. I passed him at the same time the car passed us. I rode between them on the dotted line. Scary experience!

Even without a riding buddy, a car could rear end you while they are dialing their cell phone.

[tkpinsc]

i ride with both on, the only problem i have is i dont think they are working properly, the last few long rides i had, as son as i felt a sputter, i switched them both to reserve, but didnt make it even 5 miles to a gas station..... the petcocks are new... could they have been installed wrong? i used to be able to ride at least 15 miles on reserve no prob before, even more i think, never really measured. anyone...?


Drain your tank. It's a good chance you have an inch or so of water in the bottom.

[tkpinsc]

Ride with the left one on and right one off. Fill up before a days ride and don,t worry about running out of fuel. When it sputters put the right side if on, I keep my throttle lock on so the revs go down slowly, so I do not worry about slowing down. Then reserve left and reserve right. I ge about 20 miles to each switch over and have been doing it for 32 years. Once in a great while I will go crazy and start off with the right side just for the fun of it
Later
Brian

This is my preferred method as well, except I usuall start out for a few miles with both petcocks on reserve to clear any water/sludge etc that has settled on the bottom of the tank.

[tghsmith]

running on reserve most likely will not clear out water or sludge, depending where you live, how your bike is stored, where you get your gas, how often you ride,and a long list of other factors draining +cleaning your tank and petcocks ever so often is a very good idea.

[The_Veg]

Fact: a well-flown barrel roll will keep 1G constantly while the plane is one its side, while it is upside down, and on its other side..... Theoretically, that cup of coffee would not spill, even with the plane upside down.

So, the gas should be "pressing" straight down the vertical axis of the bike as it leans into turns (exception is sidecar, as above, but they built special sidecar float chambers on the old BMW's)

How's that for physics, turns, and the state of the universe!


The gist I got was that it was one of those lower-speed turns in which the bike is leaned a little but the rider stays upright...sounds plausible. But hey, I wasn't there so who knows.

Of course these assumptions about vertical axis and which way the G's pull assume that the bike was making a coordinated turn. ;)

[Rod Sheridan]

I clean the tank and filter screens on the petcocks annualy.

I ride with the right petcock in the On position, the left Off.

When I run out of main right tank, I can use my left hand to open the left petcock. (This way I don't remove my hand from the throttle, and don't care whether I use the left main or reserve fuel). I'm not great at using my left hand, so the don't care for position is failsafe.

This leaves me two more reserves. Kind of the Belt/Suspenders/Duct tape approach to fuel management.

Regards, Rod.

[plaka]

I'm with Ron on running the right and then switching to the left followed by the reserves in sequence.

However when running on the right and getting to the sputter point, I close the right side before opening the left. This prevents fuel equalizing levels in the tank and back flushing the right side inline filter. .

Next I go from running on the left to running on the left reserve. Then in turn I close the left and run on the right reserve to prevent back flushing the left side.























O.K. I'm kidding. But I do run on one side at a time until getting low.

[rocketman]

Man, you guys are WAY overthinking this whole issue, just turn both on then when its time to hit reserve go with the left then right side. If you've spent any time on the bike you should have a pretty good idea of how far you can go before thinking about refueling. 200 hundred miles or 5 hours, which ever comes first (for the larger 5+ gallon tanks). I've never had a problem in 30 plus years of riding airheads even with ones where the odo isn't working (which died on all three within the first 40K), so I go by time and estimated distance.
Back flushing, stale gas, water build-up,all non-issues if you run both petcocks open from the git-go!

Its an airhead, keep it simple! :lol

RM

[20774]

Man, you guys are WAY overthinking this whole issue, RM

+1 :thumb

[dduelin]

My R100 will stutter a slight amount if running on one petcock and throttle WFO but most of the time I run on one and alternate which one now and then to keep both working easily.

[The_Veg]

My R100 will stutter a slight amount if running on one petcock and throttle WFO but most of the time I run on one and alternate which one now and then to keep both working easily.

I think I read somewhere that at the end of the fuel line that connects to the carb, you want to have a flow rate of at least 125 ml/15 seconds.