Atv's stall out at 1/2-3/4 throttle?

[trailrider894]

My 2000 400ex has just suddenly started stalling out around 1/2 to 3/4 throttle... it runs amazing up until that point, then just pops and cracks in and out until you hit almost full throttle. What could this be? i am running the Sparks Advanced Timing Key, but that is my only engine mod. I have a FMF Powerbomb Header and a White Bro's E-Series exhaust and also a K&N Filter with a Outerwears Pre-Filter and no lid on the airbox. I just put a new DPR8Z plug in it and am running 97 Octane fuel... Any help is really appreciated!!!

[dalejiw25]

Hard tellin. When's the last time you went through your carb.If your idle and top are good your jets are prolly good. Could be a bad needle,Bent needle,Loose needle, clogged needle jet, Pump diaphragm,Air cut-off valve,Joint pipe, or you might just need to adjust your A/F screw. To me tearin the carb. down is the easiest and cheapest place to start. Also check to make sure your choke isn't falling on while your riding. Before I took my choke off I had it tied back with a rubber band. lol. This is a commonly overlooked problem on the 400s. Good Luck.

clean the carb make sure the jets are tight. and if it still doing it dump the gas out and put new gas in it all so it could be the plug even if it new it could be defect. and thats my take on it hope it helps you.

[bigbad400]

take off ur outerwears off and check your filter. i bet its dirty as hell, if not try without the outerwears, i have seen them get plugged, like they dont get clean anymore. just checking

[honda400ex2003]

how long have you had the mods and have you done anything recently different than usual? What jetting are you running with that setup? I would say if it just started you have something clogged up in the main or in the needle assembly. dont forget to take out the housing for the needle up inside the middle of the carb, take the center assembly with the main in it out and knock the peice out, just make sure you remember how to put it back in. it is number 2 on the schematic and goes along with the needle.
http://www.bikebandit.com/houseofmotorcycles/2003-honda-motorcycle-trx400ex-fourtrax-ex-carburetor/o/m2661sch98410

make sure you clean out the bowl too and the pilot while you are in there.
steve

[honda400ex2003]

also clean the k&n with the correct cleaners and oil, and clean the outerwear with the cleaner and dont put oil on it when you clean both of them. steve

[trailrider894]

I have had the mods for a few months, but the bike hasn't even been started up more than a dozen times since then. No nothing besides the normal. And i am not sure about what the jetting is right now...

[f4iracer]

You need to adjust your needle clip setting.

The needle jet controls all of your mid range throttle which is exactly what you're explaining.

You have an older 400ex so you're needle has adjustable clip settings on it. Go down one notch on the needle and that should help.

When i rejetted my ex it was stalling out at mid and low throttle ranges. I bought an adjustable needle and it fixed it right up.

[99400esex]

Same thing happened to mine last week, I thought it was the jetting in the carb but it ended up being bad wiring for the tether switch and coil.