Ignorant question: switching to "Reserve"

[FSCGunslinger]

So... I was gonna title this thread "Stupid question...", but I've always been told that the only stupid question is the one you don't ask. So here it is:

Does switching my fuel petcocks to "Reserve" actually do anything on my XJs? Do I need to do it, or can I just leave them on "On"? What's the purpose?

I promise I'm not an idiot...

[DGXSER]

Ok, I'll preface this with I know how things work on my XS and have never looked at the XJ. On my XS, the reserve (or the prime) allows me to use the last half gallon or so in the tank.

I did not inspect the intake part of the petcock to well when I had it off, but I would think the ON position must draw fuel from a "tube" that sticks up into the filter housing a bit to stop drawing when the tank gets down so low. Think drinking from a straw that is not inserted all the way into your cup, or a drain in the bottom of your tub that sticks up an couple inches above the bottom. The PRIME and RES must draw from the base of the petcock. HTH

[CatatonicBug]

Yep. That's it. Think of it as a built-in second gas tank. The fuel level will drop to "empty", and you need to get to a gas station ASAP. If the nearest station is further than a few miles, you might run outta gas. So, then you can switch to reserve, and that will allow you to use the last little bit of fuel in the tank to get you to the gas station. The benefit of NOT using the Reserve setting is that you are taking fuel from above the bottom of the tank, and therefore not sucking the possible grime from that settles into the lowest level of the tank down into the carbs.

[FSCGunslinger]

Ah, I see, I see. Here's another question, then, since I now know how it works...

Once I fill up, if I'm just running around town (short distance), should I run it on "Reserve" so as to cycle through the gas from lower in the tank?

[CatatonicBug]

Not really. The idea is to let the grit settle to the bottom and remain there without getting sucked into the carbs. Filling the tank will do plenty to mix up the fuel left in the tank, so there's really no worry about that. It's designed as an emergency feature to keep you from getting stranded on the side of the road.

[FSCGunslinger]

Thanks guys! I've said it before, but I'll say it again... I love this place!

[DGXSER]

Do you feel lucky punk.....do ya??

Well......here is the russian roulette game. If your tank is pretty clean, that might be a thought, but I would still think no matter what you do, or how good of gas you buy, it will have some stuff in it that will settle to the bottom of your tank. Do you want to draw that into your carbs? Of course, using it more frequently will limit how much gunk is in there perhaps, but with a close to 30 year old tank, chances are, there is some stuff there already.

IMHO, I would only use the reserve when you need to. Every time you fill the tank up, the gas in the bottom will get "churned up" into the new gas your adding by the pressure and flow from the fuel hose nozzle. Using reserve would only increase your chances of getting gunk into the float valve needle valves which are sensitive, trust me, sensitive. Again, JMHO, YMMV

[TopCatGr58]

Hey there Slinger,

Aside from any sludge or debris, once you fill up, the gas all mixes together, it's just the sediment that will fall to the bottom of the tank. The petcocks have filter towers on them, so they filter out most of the larger particles, flakes of rust, etc.. Hopefully you also have INLINE fuel filters that will then catch the remaining fine rust particles that could get past the fairly large screens of the petcock filters, and could cause problems with the carbs. There is no separate chamber for the reserve, it's just the height of the filter towers and their inlet tubes that allow the fuel to drain from first a higher position in the tank, and then a lower level due to a shorter tube.

The gas in the bottom isn't going to get stale, so just run on ON, and save the RESERVE for when you really need it.
T.C.

[tarzan]

You can run it on "on" for most riding.I only go to reserve if the bike starts sputtering.
Your fuel will mix as the bike travels over bumps and turns with just normal driving,so running off the bottom(which is what reserve does) really just makes the dirt and possibly water in the bottom of the tank cycle through.
Another thing,the petcocks have a tower that sticks up into the tank.One side of the tower has a higher chamber than the other and feeds the "on" side.The other side of the towers chamber is close to the bottom of the tank accessible when in the reserve position.
And the tower has a fine built in screen that generally prevents dirt into the carbs.

[FSCGunslinger]

Roger roger! Yeah, I've got small inline filters on my black one which is the one I'm running now. Hopefully it's doing its job.

[fredintoon]

symptomless sickness

Hi Gunslinger,
now that you know how the reserve works, here's a new worry.
Sometimes the filter towers fall off the gas taps and lie loose in the bottom of the tank. You won't know it's happened until you switch to reserve only to find it's all gone all ready. Happened to me on my XS650 which has gas taps identical to the XS1100. 20 miles from the nearest gas station. Only the 2 gallon jerrycan of gas that my sidecar rigs habitually carry saved me from serious embarrassment.

[madmax-im]

Its all about not running out of gas

OK heres how I see it...if you always run on the reserve setting you wont know you're outta gas until you're outta gas. Running in the "on" position allows the tank to drain past the shorter fuel supply tube inthe tank..thus the sputtering is your warning that you are running out. That is when you switch to reserv and go find some gas... Heres the funny thing...I have owned my XJ 26 years and every new riding season this sputtering out of gas always catches me off guard at least once every year ..I wonder What the FFFF???Before I realize what it is...never fails...LOL