I did a search but could not find the info i needed. I have a stock pipe with 5, 1/2 inch holes drilled into the mid plate in the pipe (this plate must force the exhaust around to the outside of the pipe) and the spark arrestor is out, no air box cover, cam mod and the GYTR air filter. I have a 170 main jet, The YZ needle (4th) and a 45 pilot jet, 3 turns out on the airscrew. My? Is that at 3/8 throttle it pops a little (free revving no load) but nowhere else. When driving at same throttle position it is fine. Does this mean the jetting is close enough or should I go with a 48 pilot jet? Thanks for the help.
Terry

 

Anyone have any idea?

 

First thing to do is put the needle on clip 3, then put in the 48 pilot and 1.5 turns on the screw. If it still pops alittle then adjust the screw until it is gone.

 

Thanks i will try it.

 

The yfz needs it jetting runs to be under a load, otherwise yes, you get the pop burble if you just rev in N. The best way to do jetting is to set the needle on 3 or 4, whichever you need for some more mid range fuel, and adjust your main and pilots from there. Always easiest to start rich and back down one size at a time until it stops bogging on top. Rich is always easier to tell than a lean condition.