what happened?

[MtnEX]

OK so I hadn't really ridden my 400EX in a while until this month.

It was stored well, nothing in the carb and stuff.

Well, 2 times I have got it out and both times it acts real lean... Hard to crank up and keep running and very hard to get to take any throttle.

It has all the symptoms of lean, even popping back through the intake.

After a good good warm up it quits the crap...

I would assume partially clogged jets if it was parked with fuel in the carb and stuff.

Only other time I have ever seen this it was a hole in the fuel line, but I have not found one yet.

I'm kinda stumped on what to think, much less where to decide to start troubleshooting.

[tri5ron]

you say "nothing in the carb",.. but there is still some residual fuel in there that will gel/clog in the jets.

Also, are you letting it sit with the fuel in the tank, but just have the petcock turned off ?
If so,.. chances are,..
1-
The fuel is bad from sitting. (it can actually go "Bad" in a matter of a few months), depending on what your local fuels are formulated to.
(yes it can vary from one area to another).

2-
there is also the possibility that you have gel /gunked fuel, in the fuel tank and the "In tank filter screen".

Pull your petcock off, clean it out, shoot some carb cleaner through it in ALL 3 POSITION on the fuel selector lever,...and clean the screen inside the tank.

it looks like this..
http://i111.photobucket.com/albums/n148/tri5ron/03%20400ex/IMG_3512.jpg

3-
if you are trying to use that old fuel that was sitting in the tank, ... GET RID of it.
more than 3 months old, and it's crap.

Fresh fuel makes a HUGE difference in both mine and my kids quads.
But for some strange reason, my wifes 250EX seems to run fine even on older fuel. IDK,... go figure.

[DnB_racing]

also any of the rubber orings and seals in the carb do dry rot and crack after setting with no fuel for some time, its actually better to have a full tank and stabilized fuel then to be bone dry, once the seals have been exposed to fuel if allowed to set dry they crack