Hi, I did the BK mod, and changed to YZ timing last night on my '02 WR426, and i've just got back from riding, and it's like a new bike. I think it'll take a few rides to get used to the extra punch right through the rev' range. I lot of people have said they lost some bottom end by going to YZ timing, but I didn't notice it. As to your question, my '02 model had about 3.5 seconds continuous spray from the accel
' pump, I reduced it to somewhere between 0.50, and 0.65 seconds spray (my youngest son was working the stop watch, so we checked the spray duration about 30 times until we got a consistent reading between those two figures). I used those figures as an initial baseline, but the bike feels great as it is, so I don't think i'll mess with it any further. The reason I did the BK mod' to start with, was that when I was putting around through very tights tracks, on and off the throttle all the time, the bike would bog, and sometimes I could even smell petrol. Anyway the BK mod', and YZ timing combined are dynamite, I wish I had done them seperately, but it was too easy to do the timing when I already had the tank, seat and carby off. Motoman 393's site has excellent photo's and instructions for both the BK mod', and the YZ timing, good luck, Chris.