Boring, porting, and pipe! Jetting question.

Nov 5, 2016
I have a 2000 kx250 that i blew the main bearing on last season. I have now torn it apart and am in the process of rebuilding it with a new crank, rod and piston assembly off of Ebay. (Wiseco rod and crank, namura piston). Anyways, the bike already has an fmf fatty and powercore silencer and has a 52 pilot and a 160 main jet. I have the cylinder in the shop right now getting bored slightly (new piston is going to be a 67.35mm stock piston was a 66.35mm) and am having a very mild porting job done to it. I am wondering what jet sizes you guys would recommend to go with?

Ps-I blew the main bearing going wide open on the lake bed racing my buddies yz250. I'd rather foul a plug once in awhile than risk blowing it up again because this rebuild has gotten pretty damn expensive. Prior to blowing it up, the jetting seemed pretty spot on and hardly ever fouled plugs.



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