It would take alot for the KX to run a serious 1/4 mile. It would require some serious modifications including a serious set of gears and a good stretched arm. Some serious hi-rpm modifications and a good slick tire and maybe in the low-high 10s?
The KX isn't a 1/4 miler, it is an 1/8th mile bike. I can tear a new one to anything in the 1/8th. But, when it comes to the 1/4, I can't keep up due to gearing limitations.