n00b question- best practice for fuel valves

[Trials/Rider]

Do I need to run with both fuel valves open? How do you do it?
T/R

[supershaft]

No, you don't. It's a good thing too since some models only come with one.

I ride with them both open but my gas sloshes around a lot for hauling ass. Plus my bike uses a lot of gas when I am hauling the mail. Around 20mpg.

[squish]

My r80st only has one. The wife's r80 has two and runs ok with only one open.
My r100gs runs better with both open. I don't know why since there's only so much fuel that can flow into em.

Mind you that's a butt Dyna, no hard numbers to backp those claims just seat of the pants experience.

[disston]

On my R90/6 I use both. I think most of the time it would run on one but I use both all the time. I buy gas when the main runs dry I switch both to reserve at the same time. (some riders think they have two reserves if they use one at a time. I think I have the same amount of gas in the tank and see no advantage.)

[Plaka]

Originally Posted by Trials/Rider

Do I need to run with both fuel valves open? How do you do it?
T/R

With a /2, yes, and avoid going on reserve.

Everything else, if it runs fine on 1 (my 75/5, 90/5 and 100RS did) I'd run one, the right, with the left off. When that runs dry turn the left on (non-throttle hand). When that runs dry turn the left on reserve (non-throttle hand). When that runs dry you screwed up. Going to reserve on the right is a last ditch move.

Bear in mind the levels are re-equilibrating in the tank with both valves open. So you have to follow the same pattern every time to know what the distances are for each setting in the progression.

Off road with a lot of bouncing and fuel sloshing you never know how much is on either side. I'd go both on then both reserve. Throttle hand matters not, you can stop.

Snowbum has argued (w/ me) that suppose you are passing a semi on a two lane with an oncoming Ferrari and you lose power and need to switch on reserve...yeah, OK, flip the left to reserve briefly when going in harms way if you think you are near your limit.


If your bike has detonation problems when lean, turn everything on and stop before you need any sort of reserve.


I have 3 tanks now and 4 valves. I usually top up everything. Then run on the left saddle tank for about 25 miles to burn it down (leaks on the sidestand) Then switch up to my main tank only and turn both sides to reserve and run it dry, keeping the extra weight low. Finally I use all the right saddle tank and lastly the remainder of the left as a reserve. That's 350-395+ miles and I'm plenty ready for a break. I don't ride big distances at a sitting. I do run from cheap gas to cheap gas, and that can be a ways.

[bizalich]

Originally Posted by Trials/Rider

Do I need to run with both fuel valves open? How do you do it?
T/R

from one nOOb to another... i have 2 fuel taps, and run both open.

When i need reserve, i switch both to reserve at the same time and start looking for gas. Normally my butt hurts or i need a coffee before i run out of gas, but i have had that panicky moment when fuel is gone and you need to switch to reserve in the middle of a corner or on the highway... in which case i normally have about 20 minutes before i am walking.

also, i am in the habit of turning OFF both petcocks like 3 blocks before i get to my house after a ride. This way neither side leaks when it is in the garage.

Actually, now that i think about it, not sure if this is a good practice or not? Can it cause some sort of carb problem i dont know about?

[Bill Harris]

Originally Posted by disston

On my R90/6 I use both. I think most of the time it would run on one but I use both all the time. I buy gas when the main runs dry I switch both to reserve at the same time. (some riders think they have two reserves if they use one at a time. I think I have the same amount of gas in the tank and see no advantage.)

It gives you "two" reserves. It's for procrastinators-- switch to the first reserve, note the mileage. When you have to switch over to the second reserve, note the new mileage, subtract and that'll tell you how long you have before you need to walk. Do you remember how many miles you have on reserve?

--Bill

[gsd4me]

It's not a bad idea to sometimes run your tap(s) on reserve after you've fueled up, especially on big tanks that are topped up before they go onto reserve. Water can gather at the bottom of the tank and can cause corrosion but it is easily burnt off when it passes through the carbys.

[some_guy]

I got rid of the T-connectors and crossover fuel line, so I run with both on. When I had it in place I didn't notice a difference with only one on with the exception of when I was low on fuel, not empty. It seemed to starve the opposite cylinder first as if the bowl wasn't filling quick enough.

Now I just make sure to fill up at about 140 miles when I'm commuting ~35mpg and I've learned to flip both to reserve real quick when it starts cutting out.

[DaveBall]

You can run your bike either way. Under normal riding conditions, you can run with just 1 petcock open at a time. Switch to the other side when you start running out. But, realize that the other side will not have all that much more fuel in it than the original side. You will be on reserve fairly quickly. Myself, I rarely hit reserve. I know how far I can go on a tank of fuel and will fill up usually just before hitting reserve. I don't worry about crud build up in the bottom of the tank, mainly due to all the sloshing around and that I fully drain and flush my tanks every winter.

If you are a very hard rider out doing some canyon carving, I would recommend using both petcocks at the same time. Under hard cornering with less fuel in the tank, the fuel will go to the lowest part of the tank. There is a center tunnel under the tank, that will stop the fuel from flowing back to the other side, when you go from extreme lean to straight up. If you were only using 1 petcock, then you could loose fuel to the carbs.

[Airhead Wrangler]

Originally Posted by some_guy

I got rid of the T-connectors and crossover fuel line, so I run with both on.

Why would you do that? Do you want one side to run out of gas before the other? You know BMW tanks have a huge cutout on the right side to accommodate all the electrical stuff under the tank? The left side of the tank carries more gas than the right, so you're reducing your fuel range quite a bit. ...unless you want to putt around looking for gas on one cylinder.

[Trials/Rider]

This is why I asked; I rode in to work yesterday with ~ 3g or so of fuel and when I started pulling up to the house (slight grade up hill) and noticed it starting to run like crap. I pulled up to the garage to back it it and was really running bad. I have clear fuel lines on and noticed that the right side was full of air while the left side was fine? I opened the right side fuel valve and it instantly fixed the problem.

But since both valves go into a fuel cutoff solenoid, then back into a tee how can this happen if there's fuel? I'll stick something in and try to measure the fuel tonight and report back what I find. Better yet, I'll drain the one side and see if it's just starting to reach the reserve level.
I was curious what others experienced, and like Squish said it seems to runs better with both open. If I still had the black rubber fuel line I wouldn’t have seen this to understand what was going on.
t/r

[Airhead Wrangler]

I'd ditch the solenoid. It really only causes problems. Just run two hoses off your tank down to two T connections with a crossover between the two hoses. Continue both sides down off the Ts to your carbs. Done. It looks like an uppercase H.

[crazydrummerdude]

I run both on. Then I hit one reserve and take it easy. Then I hit the other reserve and start to worry.

[some_guy]

Originally Posted by Airhead Wrangler

Why would you do that?

For fun. The only time it's ever been a problem was a long corner with a nearly empty tank. If it was a problem more often I'd have put the t's back on.