Tank size

[HarryHornby]

OK, please feel free to take the p1ss if I'm being blonde here, but....
 
I was just trying to work out my rough fuel efficiency, so I looked on this site and saw that my bike should have a 20 litre tank.  It's a mk1, registered on an 02 plate, so I'm guessing one of the last box-eye ones.  According to a page on this forum about changes to models, means I've got a 20 litre tank.
 
This go me thinking..... I always fill up a few miles after the petrol light comes on (usually about 20 ish).  I fill up and it normally costs me about £21 on todays prices so about 15 litres, but a 20 litre tank should cost £28, that's quite a bit of difference.
 
Is it that the petrol light is set to come on when you efectively have a quarter of the tank left?  Seems a lot to me.
 
 

[Fazer Jake]

Most accurate way to work this out is reset your trip to 0 fill the tank from the red to full. Next time you fill up see how many miles you've done and how many litre it had taken you to fill the tank

For example =

18.46 litre 190 miles on the trip

(190 miles / 18.46 Litres ) x 4.54 (Litres in a gallon) = Your MPG 

[HarryHornby]

I'm totally onboard with the calculations it's just the tank size that's confusing me.  £21 means I'm only putting about 15 litres of fuel in (3.3 gallons).  Just seems very odd that the light on a 20 litre tank comes on when the needle is right at the bottom of the guage, but I technically have 1/4 of a tank left.
 
re MPG, I get about 180 (just under) miles for my £21 before the light comes on again, that's 54 mpg and that's with some fast acceleration, 80/90 on the 10 miles of dual carriageway each day.
 
I've recently done a little experiment on the last fill up.  I didn't go above 5k revs.  No over takes, 60mph on the dual carriageway and the light came on at 207 miles, that's almost 30 miles more per 15 litres!  WOW, didn't think it would be that different.

[know your limitations]

Next time the light comes on, take a plastic fuel can with a couple of litres in a rucksack or topbox etc. and just ride it til it's dry.
They don't just stop when you run out of fuel, you get a bit of warning with the performance of the engine.
When you get the tell-tale judder head for the petrol station.
Just pick a route that goes near one so your proper fill up is soon after you've put in your 2 litre back up (if used)
 
I've done this with all of my bikes and it invariably works out to 3 litres (ish) being left, for me that's roughly 30 miles. Plenty of warning before squeaky bum time.
 
If it turns out that you are actually getting the orange light with a quarter of a tank left, I would consider investigating the position of your sender in the tank.
 

[Fazerider]

The fuel gauge reads pessimistically on mine too, I think it's normal though there will be variation from one example to another.. it's not a precision instrument. Like yours the low fuel warning light comes on pretty early on mine too. I generally aim to hold out for another 40 miles after it comes on so I can get a decent amount in, usually 18 or 19 litres.

[Dead Eye]

You aren't going crazy, mine does something very similar. In fact I usually have over a gallon of fuel left when the light comes on. I've found I can let the needle drop to the middle line of the 'E' and I still have 1 or 2 litres left in the tank

As far as im concerned, the red light is a scare tactic to make you fill up sooner and avoid running out of fuel as there is no onboard reserve fuel

[MarchRide]

Also depends on how you fill up.

Once the pump clicks off the first time, you can usually, with a bit of patience, trickle in at least another 2 or 3 litres.

[ddtwelve]

With mine the fuel clicks off way before it's near the top of the tank I always pull the nozzle out and fill upto Tue bottom of the perforated nozzle hole inside of the tank (hope that makes sense)

[Deefer666]

On my I can get about 40ish more miles out of it when the light comes on.... probably more but I have never wanted to run it dry (cos it sucks all sorts of stuff from the bottom of the tank into the filters. The needle drops well below the E on the guage before its even close to running out.

[Fazerider]

On my I can get about 40ish more miles out of it when the light comes on.... probably more but I have never wanted to run it dry (cos it sucks all sorts of stuff from the bottom of the tank into the filters. The needle drops well below the E on the guage before its even close to running out.

I try to avoid running dry cos having to push the bike to a filling station is inconvenient.


Actually, isn't this "sucking crap from the bottom of the tank" thing just a myth? I mean, that's where the fuel's taken from all the time, for running low on fuel to cause a problem the garbage would have to be floating on top of the petrol.

[Deefer666]

No mate its no myth, believe it or not there is all sorts of crap in a petrol tank after a few years of use and normally the particles slosh around with the fuel.... Its normal. But when you run out of fuel said crud gathers on the bottom of the tank as there is no longer any fuel to slosh around in and then hits you filters in one go (not good!)

If it were a myth you would not have a seperate fuel filter and the guaze on the tap would do the lot.

[limax2]

My contribution to this debate may or may not be of interest, but here it is anyway.
This was on a 1999 bike and may have changed on the later models.
The fuel tap has a 40mm long stand pipe on it, which is sticking into the tank. Most of this stand pipe is mesh which provides some degree of course filtration. However the bottom 14mm has a plain surface which fuel does not flow through. The result of this is that there is 1.5 litres of fuel in the tank that you can't use. (That's with the bike stationary, so when riding and the fuel is sloshing about you will probably get a bit of it.)
On a test sample of one, a further 2.3 litres of fuel was required before a change was seen on the gauge.
On my 2001 model :-
 5 litres of "usable" fuel shows just under 1/4 on the gauge.
10 litres shows just under 1/2 on the gauge.
15 litres shows off the scale.
 
 
 

[Deefer666]

Ahhh so if you do away with the mesh on the tap (FZS600s have very good fuel filters fitted) you could get more miles to the tank?

[Dead Eye]

The way i read it is that the mesh isnt the problem. Its the solid 14mm of pipe at the bottom where fuel cant get through - you would need to make the entire 40mm pipe out of mesh instead.

[limax2]

The way i read it is that the mesh isnt the problem. Its the solid 14mm of pipe at the bottom where fuel cant get through - you would need to make the entire 40mm pipe out of mesh instead.

You are right, but I think what Deefer was meaning was to do away with the plastic pipe completely.
The 14mm is probably there to prevent drawing any of the crap previously mentioned and also any water that would sink to the bottom.
A way to increase the capacity a little, which has been mentioned before on the site, is to drill a breather hole part way up the tube that sticks into the tank below the filler neck. This allows more fuel in the tank by reducing the air space above the fuel when full. Of course you try not to get drilling swarf into the tank when doing this mod.
I find 200 miles is enough range to keep me happy so I haven't done any of these things  .