My friend took the emission canister out from his KLX and plugged the vacuum hose that came from the airbox and pulled new hoses from the tank overflow and tank breathing connector to underneath the bike. Easy mod, saves you about 1kg from the bike weight and it looks better.
BUT, BUT, the end result is that now his bike is using 0.5 to 1 liter more gasoline per tank than my KLX. We drive together the same route and distance, I fill 5liters on the pump, he fills 5.5 - 6 liters. Before the modification we used the same amount. The extra fuel actually drains out from the bike. Especially off road it seems the gas is splashing a lot in the tank and end up to the overflow & breathing pipes. Especially if you fall over, you better pick up the bike fast as the gas is leaking. Normally the emission canister will collect the gas and return the gas to the tank when the engine is running.
With KLX this is an issue as the tank is small and sometimes you need all the range it can give. Also the puddle of gasoline under the bike after he fills the tank is a fire hazard.
I guess there is a better way to remove the canister as for instance the KLX is sold in Indonesia and Japan come without the emission canister? I think just plugging the overflow & breathing pipes won't work as the tank might collect over pressure?
By looking at the design of the emission canister, I think it has no effect to the engine performance as long as there is no leak in the vacuum pipes, so I will not remove mine before figuring out the correct way to do it.