I have heard about it but as KX tanks are high instead of long I don't think it would make much difference.
Plus it would make it a real pain working out how much petrol is in the tank.
The KX tank is more tall than wide, but still on braking/throttle transitions I think the fuel can slosh around quite a bit
The tank on my bike is about 4 gal, its an aftermarket tank, it came with the bike when I bought it....
But, the average sportbike / racebike weighs 400-450 lbs with fuel. Lets say 5 gal of gas, thats about 30 lbs of fuel (about 6 lbs/gal)
The fuel is then only about 6-8% of the total weight
But a KX500, lets say 240 lbs fully fueled, with 3-4 gal of gas (stock vs aftermarket), thats 18-24 lbs of gas, thats 7-10% of total weight
So, using very rough estimates, the KX has as much or more weight, proportionally, in the fuel than the sportbikess, so I'd think weight transfer in the fuel would still have some effect
Also, the sportbikes are going FAR faster (a slow corner on the race track is probably 60 mph.... fast ones could be 140+), and the bigger heavier wheels are going ot have a lot more gyroscopic force than a dirtbike will ever have, so its going to take more weight/force to effect it
But, dirtbikes ride on far rougher terrain, so the bike is going to be pitching about a lot more on its own....
*shrugs*
same old story, something is useful in one place, and it might be useful in another, but there are about 10 factors making the second situation different
I'm getting some foam for one of my streetbikes (possible trackbike), I'll probably just throw some in the KX, see what it does.
Good point on making the fuel harder to check, I've though of rigging a clear tube to run along side the outside of the gas tank, along the side, so it would be easy to check the fuel level while riding (i've got a white aftermarket gas tank on the bike, but its still near impossible to see the fuel level without removing the gas cap). This would be handy even w/o tank foam. will post on this in the future......