BK mod and jetting

I have a wr450 that is uncorked but waiting for Dr. D exhaust. Does the BK mod work on 450's? If anyone has got the jetting down for 8000ft. I would like some info. I have seen the Larryco posts and if jetting for the 426 will work for the 450 I will go for it but I would think it would be alittle different.


I'm at 9,100 feet with a new wr450f. My latest jetting is light years ahead from stock, but it's only been tested around 50 degrees. Key: Replace needle with stock YZ450 needle and put at 4th position from top. 155 main, 42 pilot, air screw 1 3/4 turns. Pipe is SuperTrapp with 6 discs; about 96 db. What's a BK mod?

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