rholt400ex
09-01-2010, 08:08 PM
hey i have a 2000 400ex. i bought this quad a year ago stock and i have put on a k&n air filter without lid, full exhaust system and a 170 main jet with the a/f screw 3 1/2 tuns out. quad has ran great and strong for months. i have always kept up on it. change oil, adjust valves change plugs. whenever i found something wrong or heard a noise i would always fix or replace it.so its been well maintained since ive had it. new axle bearings swing arm bearings stem bearings chain sprockets and so on. well the other day i CHECKED the valves they were good changed plug and oil. bout an hour ito riding it and it started to sputter (like misfire) at 3/4 to WOT and seemed to get worse the more i rode it. so went and cleaned carb throly still did it. checked carb again even tried changing up the jets few times. still did it. pulled the plug and it was BLACK. and i had two hours or so use on it. i know it sounds like im running rich here but i know it cant be the carb. it has ran great the 6 months the jet kit was in. then tried changin the coil. still did it. and yet the sputtering or loss of power is gettig worse like 1/4 to 1/2 throttle now and cant get past there. the bike starts and idles greateven a few small revs sound good and no smoke at all ever. so yesterday i did a compression test it was exactly 125psi which is good rite?