Originally Posted by bmwhd
The KLX250S has a different crank vent setup than the KLX300R. The 250 already has in effect what results from doing the mod on the 300. In fact, the entire airbox setup is very different between the two bikes due to the fact that the street legal 250 has to have an air injection system grafted on to it for the EPA.
Can you explain what you are saying? re: 'The 250 already has in effect what results from doing the mod on the 300.'
I'm saying the 1" crank vent hose to the airbox is restricted internally by a plug which only has a 1/8" hole in it. This in effect causes a crankcase pressure & vacumm because it can't breath fast enough at higher rpm. Remove the plug and voila... it revs freer.