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View Full Version : Uncommanded weight shift = bad..my $20 fix!



joeblow
12-04-2011, 09:31 PM
OK some of you followed by tank reseal job (now complete) and my second job while I was in there redoing and improving the tank heat shield and sound deadening. This is the other 'opportunity' mod I made while the tank was off.

As I mentioned in one of my other posts, I am an old racecar driver and a lot of what I do comes from that. If this has been covered before, I appoligise and hope I am adding something to it or at least a few pics. So here I go!

It is no mystery that the fuel is a liquid..duh! Well being a liquid it sloshes around in our tanks. This sloshing causes a weight shift to the tune of roughly 6lbs per US gallon (7lbs for our UK Brothers). So if we have burned down one gallon and have around 4 remaining that is 24 lbs of weight change!

Now lets imagine we are on our favorite back road with those long sweeping corners where we roll in and as we do the fuel sloshes to the inside, then as the bike takes a set it sloshes to the middle and then the outside. That is a lot of fuel moving around (25@ if you recall).

What about a more dangerous situation (just happend to me last night by the way). Idiot driver pulls in front of you and you have to do a quick Rt/St/Lt maneuver to keep from hitting her or the guy in the lane next to you! That fuel is going to slow you down as the weight of the fuel if fighting you as you transision quickly. Not good.

So I decided to fix that. We use a foam called fuel cell foam all the time in auto racing for the same reasons as above plus it reduces the chance of fuel starvation in cars which lean the wrong way in the corners ;) So here is how I did it:

First I took a block of foam I had from one of my race car projects. The size of the block was roughly 1 SqFt give or take. This much foam at a race shop is less than $20. It is important to use racecar fuel cell foam as it is a large cell foam so it does not reduce the tank size much at all. It is also impervious to fuels including some of the nasty stuff I used to use ;)

My initial plan was to cut two small blocks for the sides and one for the center but I found the single large block too hard to work with and with two I could more easily route the fuel lines. So the rest is pretty self explanatory in the pics. The end result is a tank that drastically reduces the sloshing and keeps more of the fuel at the sump during aggressive braking when they can be starved with a low tank.

A couple of notes...you do not want any of the foam under the sump plate where it can get tangled in with the pump and such. Two, be aware of the fuel lines as if they are folded over somewhere they will be pinched off...not good. Lastly, if you are in there change the vent and drain hoses. They were pretty nasty on my bike. It has been recommended to use a special gates hose, tyco (sp?), but I used Motion Pro 1/4" which is undersized from the 6mm original stuff. It was so tight fitting I am sure I could have left off the clamps. It is 100% fuel safe inside and out.

One other little trick I did was to label the lines (V=Vent D=Drain) so that when I was fitting the sump plate I did not have to guess. I put the same letters on the sump plate. I don't like trying to figure that out with sealer on the sump plate while balancing everything!

Good luck!

hoffmanmark
12-24-2011, 10:15 AM
Just curious, what year bike do you have? How much gas is displaced or is the foam open enough that it does not make much of a difference? I will be buying my brothers 02 mille r and would like to make this mod if possible. Thank You

deefred
12-25-2011, 05:17 PM
Make sure you use a high quality foam if you decide to do this.
Cheap stuff can detoriate and clogg the fuel filter.

When I was racing we had to use it as it can prevent tank explosions.

hank
12-25-2011, 05:25 PM
http://www.apriliaforum.com/forums/showthread.php?t=237212&highlight=tank+foam

PumpinIron
12-25-2011, 06:02 PM
I assume this foam is some sort of foam that doesn't deteriorate due to the ethanol in pump gas?

joeblow
12-25-2011, 07:38 PM
I have an 00' bike (steel tank). The foam takes up nearly no volume as it is very open cell.


Just curious, what year bike do you have? How much gas is displaced or is the foam open enough that it does not make much of a difference? I will be buying my brothers 02 mille r and would like to make this mod if possible. Thank You

joeblow
12-25-2011, 07:41 PM
Correct, almost all of it is alcohol safe nowadays but back in the day I would just buy the stuff made for ethanol racing fuels (ie. 100% ethanol!).


I assume this foam is some sort of foam that doesn't deteriorate due to the ethanol in pump gas?