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What exactly is 'the reserve'?

Discussion in 'New Riders and Riding Tips' started by Spud Gun, Feb 26, 2005.

  1. I was riding up Oxford Street in 5th doing about 6K revs when the engine revs start dipping, I drop a gear and still the engine revs keep dipping. This happens as I drop through the gears until the bike eventually stalls. I started again and off I go but I still get the engine revs dropping off until I got home about 5 mins ago. I have never run out of petrol but I am assuming thats the problem. I open the tank and shine a tourch into the tank, and I have about 4cms of petrol in the tank. Is that the reserve? I always thought that the reserve was somewhere else, but is it just the lower part of the main tank? Is that what I can expect when I run out of petrol?

  2. Yes and yes 8)
  3. Phew! Thanks for that! I saw dollar signs appear for a few minutes. So the main tank has an overflow (whatever the techie term is) that set higher than the reserve overflow? I just got the bike back from a service, but I left it in with the tank 3/4 full! I know they test rind the bike after working on it but to run the tank almost dry? Man, thats a bit bloody cheeky on their part!
  4. Totally correct. The important thing to notice is how many kms since your last fuel stop. That way you get an idea of when to refuel before running out of juice. The reserve is handy but shouldn't be used too often.

    Also VERY IMPORTANT to make sure when you refuel from reserve you make sure the fuel tap is off reserve. The last thing you want is to run out of fuel and reserve fuel at the same time. No matter what bike you ride, pushing it to a servo sucks.

  5. Is the reserve just an overflow from the main tank ??? if so what difference does it make if the tap is on reserve or main tank when refuelling??
  6. oh ok...so tap position doesn't matter when refuelling then?

    How often do people take the tank off to clean the tank out? I mean all the gritty bits and glug and scum would be at the bottom in the reserve, wouldn't it? Bikes don't have fuel filters do they?? (how come??)
  7. Most sediment and water will sit at the bottom of the tank. If you never go onto reserve, then that crud will most likely never enter your carbies/fuel system. If you do a lot of miles, then constant refueling usually ensures that your tank will stay pretty clean. Of course, if you fuel up at some servo which has dirty tanks, and they've just been topped up, a lot of crud may still be swirling around and the bowser could pick it up.

    Most fuel systems have filters in them. If they don't, then it's probably a reasonable investment to have one fitted.

    And not all bikes have a reserve system. My Kawasaki ZZR-1100 didn't. It had an on/off tap that was inaccessible, and stayed permanently on. Reason for this is that it had afuel pump. Pumps don't like being starved, so the tap was meant as a maintenance thing, when removing the tank.

    The bike relied on a low level switch to illuminate a warning light (actually 2 lights that flashed like blinkers and were damned distracting) when hitting "reserve". Like most bikes of its size, this happened when there was about 4 litres (out of 22/23) left.

    My current bike, a Honda CBR1000, has an on/off/res tap. No vacuum function, which is good, as it's one less thing to stuff up. A mate's VTR's vac. tap ruptured a diaphram. Caused him to have slow 130 km ride home recently.
  8. Initially.

    My CBR has a fuel gauge with "res" and a red band where it comes into effect, as well as the reserve tap. I like that idea, as it means that you don't have to rely on an instrument that may be out of calibration. Thing is, the Honda's fuel gauge is spot on. When it hits that red band, the thing does get to the reserve limit.

    The ZZR didn't have a fuel gauge. Later models did, but I don't know if they had low level warning lights or not. Be handy if they did. Something to come on (and not flash), to remind you that you are on "reserve". At least with the tap you get a mechanical reminder.
  9. Fuel injected bikes don't have reserve taps, just low fuel warning lights, the pressure pumps used for fuel injections system do not like to be run dry on a regular basis, when your on a fuel injected bike and the low fuel light comes on, take notice your usually down to about 50kms from walking
  10. is it okay to fill up or rather top up the tank before you get to reserve?

    i went for a ride the other night (btw i've done 220km on my 1st bike ever) and i thought i'd be down so i pulled it to top it up like you would a car, but it seemed to idle a tad funny from then on (the last day or so) and a mate said that you should let it hit reserve before you fill it back up cause otherwise you swish around all the sediment or something??

    a tad lost.. any advice?
  11. Your mate's wrong. If it's small sediment, then it will get picked-up by the filter. Any larger, and it will stay in the tank no matter whether you wait till reserver or not. If your putting in teh same fuel (or even same type) then it's fine to fill-up. If you putting in different fuel, usually better to wait till you hit reserve so as you aren't mixing it.
  12. ah that might be the prob... i work at a caltex and i put in a whole tank of vortex (got 94 octane but injector cleaner and stuff) and then when i topped up i put in some of that mobil 8000 98 octane stuff so i'll just wait till it drains and got back for some 98 octane... thanks for that
  13. It makes no difference where the tap is when refueling. However if you forget to put it back to the main supply, you will have no reserve (having already used it) the next time you run out of fuel.
  14. How accurate are the fuel guages? I was under the impression that the more expensive bikes have them, and the odd 250 (bandit). Are you not more liable to run out of fuel on hot days with the higher (and misleading) fuel readings you get? At least with the valve system, when you switch over you know that you have 100K's (or whatever) left.
  15. Spud,
    A 20 degree rise in fuel temp makes less than 10% difference. Remember the old chemistry PV=nRT. The 'T' is always measured in Kelvin, so the difference between 283K(10 C) and 303K(30 C) is not really that much.
    As for Guages, the small amount of fuel sloshes around a fair bit so its difficult for any guage to get a good reading. There indicative at best. Even a reserve switch will come on at wildly different points depending on where your riding at the time. ie..climbing a hill it will cut out early.
  16. ... sorry nalasrob, PV=nRT is for ideal gases... but the point you make is right.The volume won't increase a whole heap.

    Just expanding on some of the tips so far, here are some I live by...

    1. know your tank capacity and how much of it is reserve [see the manual]

    2. always fill the tank to the same point and make sure your tap is "ON" [i.e., not on reserve!]

    3. Set the trip meter to zero.

    4. know the typical range that the bike will get to before you hit reserve. (On my '02 9R, that's about 230km's city/highway).

    5. when you hit reserve, reset the trip meter!

    I basically use the trip meter as a surrogate fuel gauge. When I'm up around 200kms I can expect the engine to start hesitating soon - no drama in a straight line... very dramatic in a corner!

    When I go to reserve, I know I have about 60kms to get to a servo before I'm dry and pounding the pavement. Short shifting and gentle acceleration will strech the reserve to about 80kms... but then it starts becoming an episode of Seinfeld!