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Work out when my bike (Suzuki GSF250V) runs out of fuel

Discussion in 'Technical and Troubleshooting Torque' started by bonkerrs, Dec 18, 2010.

  1. I believe my fuel gauge is not very accurate. So I want to do a test. Basically, I am going to ride a full tank until it runs out to see the exact position of the fuel gauge needle and how many km's I've ridden. I know, the amount of km's is subjective to riding conditions, good to get 'close to running out' figure anyway.

    Before I go out and try my experiment, I would like to know how the reserve fuel works. My tank total is 15L, that includes a 3L reserve.
    Where is the reserve kept... in a separated portion at the bottom of the tank?

    When I run out of juice I'm thinking the fuel line and carby will also be empty. After I switch over to the 'res' position to utilise that portion of fuel...
    What do I need to do to put fuel back in the fuel line and carby?

  2. I don't know your bike specifically, but basically the way reserve works is your fuel tank is a single container but has two offtake points one for normal riding and one for reserve. The normal riding offtake is at a higher point than the reserve so when your fuel drops to that level you can't get any more fuel. You then switch your tap over to reserve and it takes from a lower point below the level of the fuel you have left so fuel starts flowing again.

    Obviously you can check your range by running as far as you can before you hit reseve or hit empty and seeing how far you get. But you don't need to run your bike out of fuel to work out how far it goes.

    All you need do is fill your tank, set tripmeter to zero and ride for a while, preferably a decent distance to even out any variations in fuel usage due to hard riding, hills, wind etc. Then fill up again trying to get your level in the tank as much as possible to the same level as before. Take note of how much fuel you have used (if the servo doesn't have a docket with the fuel used on the receipt, then fuel used is the cost you paid divided by the price per litre) and how far you have travelled.

    Divide the distance travelled by how much fuel used will give you how far you get to a litre and then since you have an 18 L tank mutiply that by 18 should give you your range. Also multiplying it by 15 should give you the range to where you need to switch to reserve.

    On some bikes fuel flows purely by gravity and you just need to switch over to reserve position and your carby bowls will fill by gravity. on other bikes fuel is actively sucked into the carby bowl by vaccuum when the engine is running. On these bikes, if the carby bowl is empty, it may not fill without the engine running and without the bowl fill the engine won't run - Catch 22. So these bikes have a prime position to allow the bowl to fill by gravity, and get the bike started again. And usually the prime position on these bikes is in the tap off position on the other style of bike, so you need to know which your bike is. I don't know, so read your handbook or check with other GSF250V riders how your taps work

    Because the fuel tank is a single container if you do switch to reserve, make sure you switch back again, otherwise if you run out you will have run right out won't have a reserve to rely on.

    Ideally once you know how far you get you should be looking to fill before hitting reserve, because crap from condensation, dirty fuel rust etc in your tank, sits on the bottom and ideally you don't want to suck it in, at least not in large quantities.

    Some people also like to occasionally switch to reserve and run on that for a bit after filling to flush out any crud in the tank that may build up around the reserve offtake point, that way if you do need to go to reserve you know it won't be blocked. Probably unlikely but not a hard thing to do occasionally to be sure.
  3. GreyBM. Thanks very much for your detailed post and hitting very point/question.

    Good suggestion, use a little maths skills instead of riding till empty!
  4. Fuel consumption depends on a lot of things like riding style (when you shift), how well the engine's tuned, rider size etc., but something in the 5-6l/100km is around normal. I used to have a very similar bike (same engine and tank capacity) and for highway riding I used to aim for around 240-250kms between fuel stops, knowing that I could probably push to 300 if needed.

    I prefer to avoid using reserve myself, if there's crap in the tank it's best to remove the fuel tap and flush it properly. Also an idea to fit a filter on the fuel line itself in case the one in the tank ever fails. Small in-line filters can be picked up in auto stores for only a few bucks which is cheap insurance against getting stuck on the side of the road (more than likely your fuel line is well past the point at which it should have been replaced so best to do that at the same time).
  5. Just fill up the bike, set trip meter to zero then fill up again when you hit 100K.
    You then know how many liters per 100K.
    Do it a few times over different riding conditions, get into the habit of setting your trip meter to zero on every fill and you'll soon enough know when to fill up.

    My gs is always around 4 liters per 100K.
    It has a 20 liter tank where 4.5 liters is reserve so I usually fill up when I hit 350K.
    I have let it go a few times until I needed to switch to reserve and got over 400K a couple of times.
    On group rides I usually refill sooner as you may as well fill up when others do.

    As mentioned, reserve is only a different fuel line coming from the same tank.
    This simple diagram explains how most work.
    When your petcock is in normal fuel/on or whatever you bike says, fuel goes down the tube which is as high as the top of the green line.
    When you switch to reserve, it'll then start using the tube that goes to the top of the red section. (yellow arrow)

  6. bikes are meant to be ridden all the way to reserve and then switched. After a bit you will notice as the bike gets close to reserve the bike runs rough and you will learn to switch before the bike actually stops.

    If it does stop there will likely be a "pri" position on the tap. Put it on that and wait for a minute. Then start and switch back to on.
  7. So, set your odo to zero, then run the bike to reserve.

    You have 12 litres to reserve (15-3), so divide the litres used by the klms & presto you km/l of your bike.

    Then, times by 15 (total litres) to get a rough* distance to empty.

    For my bike: 300km to reserve using 15 litres = 20km/L

    18 litre tank, so 20*18 = 360klm till empty.

    *Your fuel consumption may (will probably) vary depending on how you ride the bike, my 250 didn't, but my TRX does...

  8. Thanks for the diagram... I'm an understand visuals better person!!

    On the GSF250V the 'pri' position is set past the 'res' position. So to get to it you have to turn clock-wise from 'use' (or 'on') to 'res' to 'pri'. There is a screw between 'res' and 'pri', I guess it is there to prevent accidentally switching it to the 'pri' position.
  9. I've been thinking about this method. If I go back to the same petrol station and use the same pump with the bike on the same lean (this part is obvious:D) it should fill to the same level. For an accurate result. Do you think the 'click' on a pump nozzle would click at the same level each time?
  10. Personally I would just do it visually. Fill to the same point using a ref like the lip of your tank. Even if it is not exactly the same by the time fuel is there you are only talking a few millilires of difference in a full tank of fuel. Franklly you will get more variation due to the way you ride, wind etc. than from filling a few ml differently.
  11. Agree with what Grey said.
    Just average out how many liters per 100K over a few fills and you'll get to know your bike soon enough and how it varies due to how the bike's being ridden.

    Like mine, under normal riding, I wait for the trip meter to get to 350K then I pull into a servo and fill it up and religioulsy reset the trip meter to zero.
    But when riding with a group, I just fill up when everyone else does unless I know the next fuel stop is within range for me to wait for the next stop.