400ex problems...

[thebutelr]

Hey guys I just recently purchased a 2002 400ex. The bike was running pretty rich when I got it and would load up on fuel at low rpm's and would leave the plug smelling like gas and wet looking. I took the carb off and found it had a dynojet flat head type jet in it labeled #142. I put the jetting back to stock with a #40 pilot and adjusted the valves but in the process of doing this the bike started to run really bad. I have the bike to where it will idle fine and rev up without any problems while it is sitting still but as soon as I start to ride it will cut out and cough & spit through the carb if I keep it in the 1/8-1/4 throttle range for very long. I installed a new plug and went riding for about 10 minutes and looked at it and the porcelain is white and the tip of the plug looks grey. Just for kicks I installed a #180 main jet I had laying around and it did not make much of a difference...still runs about the same. This seems like an air leak to me but I cannot find any cracks in the intake boot and I have not touched anything else on the bike. Any ideas on what is causing this?

[jensenracing77]

if it has the dynojet kit in it i would take all that out and trash it. but that is just me. you will want to check the needle also. if they installed the clip in the wrong place it will affect the mid throttle badly. is the engine stock? exhaust/air filter? if it is all stock i would get a stock needle and jets (148 main and 40 pilot) and put in it and start there. if it has exhaust and filter only, go with a 42 pilot and a 152 main. use the stock needle and keep it in the middle. if there is more to the engine then you will have to do more jetting but this gives you a starting point. also check the timing between the slide and the butterfly in the carb. they should open at the same time and reach full closed at the same time. also the roller on the pump will wear out sometimes. i would also check the valve adjustment.

[thebutelr]

Hey thanks for the reply. I found out after cleaning the carb like mad that my gas was the problem. It looked really cloudy so I poured some in a clear plastic cup and the gas was separated half & half! It was a golden color on top and a white/murky color at the bottom. Runs like a champ now!