Hey what is the stock front sprocket size for a 400ex?And what size sprocket should i get if i have a K&N filter and jet kit and a white bro's e series slip on that wouldnt hurt my bottom end to much????thanx

 

15 is stock. You could get a 16, but you would have to grind down your casesaver to allow for the bigger sprocket.

Adam Smith

99 400EX

 

If I understand your post correctly and you want more bottom end, go with the 14 tooth it makes a world of difference.
I can climb hills now that I used to bog with the 15.

 

no i want a bigger one for more top end?? so i can keep up with my brothers banshee on the road.

 

go with he 16 on the front and you will stay stay right beside a stock one in 1st 2nd 3rd gear but after that you will leave it in the dust. so no your bottom end will not be hurt, it calms it down to about stock which is still a lot! but puts about 7 mph on it top end! if his banshee is stock he has seen a bad day! read my article on how to fly for 30 bucks, i have two and have done the testing! let me know how it does! just grind your case saver bracket to fit, a thirty minute job,chain will adjust to fit and thats it. the best,quickest mod you will make! Renthal has them.