how does the fuel reserve work?

hello, ive got another question:

i was google searching what the reserve setting does on the petcock. i read that the reserve setting just allows fuel from the bottom of the tank to get into the carb. so it doesnt affect performance at all right?

however i also read an article saying that to drain the fuel tank you should have it on reserve so "more air can get into the tank" which will drain it faster. that implies that the reserve setting has a different function than the on setting.

the reason im curious is that now my moped only starts on reserve. does this just mean i am low on fuel or is there a problem with the moped? its a batavus btw

which is it? thanks

Re: how does the fuel reserve work?

you are probably just low on fuel.

Re: how does the fuel reserve work?

Uh try putting more fuel in and then you'll know. Could be the straw on the petcock is clogged. Gas flows faster on reserve, generally, but this has no effect on performance because the flow rate from the tank is not a limiting factor on gas getting into the engine.

Re: how does the fuel reserve work?

it means that your petcock/fuel tank is messed up. The reserve is just a seperate hole with a mini tank at the bottom of the whole gas tank. It acts as a little seperate storage unit when the rest of the gas tank is empty. When the petcock is on, the hole seperate from the reserve and connected to the rest of the gas tank is open. When it's on reserve, it is connected the reserve hole which has all the gas plus the gas in the reserve tank. I'm pretty sure there is no difference in rate from hole to hole but I could be wrong.

What I think is that either your petcock is broken or somehow you clogged the hole for the on position. Drain your tank by putting it in reserve and then take the petcock off and check it out.

Re: how does the fuel reserve work?

^ does not know how the reserve works on mopeds.

take a gander:

Re: how does the fuel reserve work?

Yeah peter that is completely made up.

A petcock has two holes in it. One has about a 2" long straw in it, the other does not. on the ON setting, fuel flows through the straw and out the petcock. On reserve it flows through the hols with no straw. So on ON you will run out of gas with about 2" of fuel left in the tank, and then you switch to reserve to use those last 2 inches and hopefully make it to a gas can.

Re: how does the fuel reserve work?

Dan: that is the article i read up on, but i wasnt sure if it was the same for mopeds cause thats for motorcycles.

so my original thought was correct then? the gas flow out of reserve and on setting is the same? i couldnt start my moped on ON because there wasnt enough fuel?

Re: how does the fuel reserve work?

Yeah, I guess I'm wrong about how it works on mopeds (they don't have the separate tank beneath) but that is how it works on my grandfather's car from the 40's as it doesn't have a gauge. Either way in both cases the reserve just uses all the gas whereas the main hole doesn't access all of it.

Re: how does the fuel reserve work?

how hard would it be to make this straw longer to give me a longer reserve period.

my tomos sprint is hard to tell how low i actually am umtill i run out and turn to reserve.

it is scary to be 15 miles from home and be one a .06 gallon reserve.

Re: how does the fuel reserve work?

dude. just keep your tank full.

Re: how does the fuel reserve work?

DUH...and if you do not know if you are low on fuel look in there? God not to be mean but how though is that? I should not have to say this but do not use your lighter for After every ride I just refill tank, I keep a 5 gallon can of premix for each running moped I own(because they use different fuel ratios) and I just top them up after every ride I have not needed to use my reserve since I was 16!

Re: how does the fuel reserve work?

OK, keller, it's not so simple as that. Just look in there. At least on MY tomos tank, you can't see into it more than an inch or two thru filling hole. It's dark and at an angle. Drive more than a mile or so and you can't see any gas.

and at least on the arrow, the reserve will get you about 15 miles. You're cutting it close, but if you're planning on being out for a distance, just fill it up before you leave. It's not usually a big problem

One thing you can do, if you have disabled your injector but not removed the tank (this is not an injector removal post!) is you can reroute the oil lines, add a petcock to them, and fill the old oil tank up with gas. Then when you run out of gas in your tank you can just let the gas from the oil tank flow into your gas tank. Give yourself a bit of a buffer.


Re: how does the fuel reserve work?

oh. my moby has this nice long dipstick on the gas cap.

but yeah, if you know about the range a tank will take you, just don't plan on exceeding that without refilling.

top it up after every few rides.

come on, not hard.

Re: how does the fuel reserve work?

who ever said the last time they had reserve on was when they were 16...

my age is? lol

and sometimes i dont have the cash for the texas tea.

so i find change under the couch.

i think i just hijacked this post sorry

Re: how does the fuel reserve work?

I said that, lol because that is the last time I ever used the reserve, even at 4.00 a gallon that should be between 60 and 100 miles of riding, if you can't afford that? Is this not why we ride these things? well they are fun...

Re: how does the fuel reserve work?

well you have me there as I have never owned a Tomos, in my Hobbit and my 50v you can see inside the tank, so my bad with regard to Tomos riders! mea Culpa! But just Top up every time you get home from a 5 gal can of premix and you never need to wory of if you are going to excede the range of your tank carry a can of premix with you? Not too deep people!

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