Hey Everyone,
Would any of you know what kind of power increase I would have if i instaled a complete White Brithers R series Exhaust,A K&N Power Jet Kit. What I am really trying to figure out is how many mph's this will add and how amny more horses the 300EX will have after mods. I should have all of these things on my quad by January along with some Itp Holeshot tires and rims. If you have any other suggestions that would work better for my 300EX please tell me.
Thanks Alot,
David

 

David,

You will notice a slight increase in power but it will not help by much. [2HP at the very best]

If you get the items you listed above along with a high compression, then you will get a substantial gain. [Roughly 5HP total]

The one item that I have seen make a big difference on the 300EXs are the timing advance flywheel keys offered by Curtis Sparks and others. They make a noticable difference in even stock engines. They cost about $20 along with a new side cover gasket from your dealer which will cost about another $20.
These flywheel keys have gotten a bad rap from owners of other quads. Blame it on engine design, because they do make a difference in the 250X/300EX engines regardless of other modifications.

Also......Take the slack out of your throttle cable if you haven't done so already. When new, like the 400EX, the cable is adjusted so that the throttle slide doesn't open all the way. This alone will make a night-and-day change to performance.