eric gorr did a big bore 99 kx125 for me (144) running on c-12(actuly its a close friends bike) and it rips he is very happy with the power it is very fast and easy to ride HUGE improvment over stock the best money he could have ever spent on his motor .but heres my question if the riding is very fast the bike rocks, but if it gets a little tight the bike wants to foul the plug very easly the main jet seems right on the bike runs great when its wide open and after doing a plug chop the plug is light tan. i tryed raising the needle clip from the third to the second clip but if i do so the bike losses throttle responce and also has a slight bog when the throttle is opened quick so i went back to the third and tryed a smaller pilot jet with the exact same results ...bog when the throttle is opened quick i even tryed a bigger pilot with the needle clip in the second clip but it still had the bog (of course while doing all of this i tryed adjusting the air screw also)if i jet the bike so it has awesome throttle responce and makes the best power it runs great if you can keep the bike wide open a lot but when the trails get tight after a few minites it wants to foul so i was thinking of trying a br8eg instead of the 9 hoping to keep that jetting that gives this bike the best throttle responce and power but with less fouling has anybody tryed this? and will this hirt his engine (detionation from too hot of plug?)if anybody has any information on this (especially you eric gorr :worship: after all you would know best you did the motor work and what a job you did.i really want to try a hottor plug but i want to be positive i will not damage the motor.please let me know what you think i should do.thanks to all who reply.