I have a 2003 400ex, it sat for about 2 years. It has Dmc Comp full exhaust, K&N air filter. I have a 155 jet in it. It runs with the choke on but when u turn the choke off it shuts off.... Please Help. By the way I just put the Jet in.

 

Iam still dealing with the same problem... Dirty carb

 

I found a new Carb on E-bay for $158, was thinking about buying a new one

 

hi, its in your best interest to take the carb you have now and take it apart and clean it well, get very thin wire and try and push it through the tiny little holes in the jets, there the size of pins very tiny, then check your air mixture screw, should be 2.5 turns away from bottom, put on a new plug and try it..you may have to finely adjust the screw to get that perfect idle

 

bluebead442 is right u shoud clen the carb

 

I agree with the others. Gasoline turns to varnish in as little as 30 days. You have varnish in the carb. Spend your money on a new carb if you want (after all, it helps keep the economy strong), but you simply need to clean the carb you have.

 

It helps keep economy strong...ok!

 

Your pilot jet and / or the passage going to the carb throat is plugged with varnish. My son's 300ex sat for 2 years in storage ( he got another quad, and I moved) same thing, would start with throttle, run with choke, but turn off the choke or let off throttle, died. The pilot circuit provides all the fuel for idle, your main wont add fuel until you start to open the slide. Pull the pilot, you may need a wire to poke out the crud, then soak or blast it with carb spray, then make sure you can see liquid come out when you put the spray can straw into the pilot hole in the carb and blast that out good too.

 

Once a carb gets varnished up the ONLY THING I've found to get the job done is Gunk brand carburetor parts cleaner. It comes in a gallon can (looks like a paint bucket), you can get it at any auto parts store, take the carb completely apart, put all the parts in the basket in the can, (no rubber or plastic parts) dunk it down in the cleaner and put the lid back on, let it soak for a couple or three days, then take it out and wash the carb and loose parts with your garden hose sprayer, blow everything dry then spray good with a can of carb cleaner then blow dry good again. Reasemble the carb, set your air or mixture screws and she will run like new.
I've been working on carbs for 30 years & have never found a better product for cleaning varnished up carbs. I don't mean to be plugging for Gunk here but I haven't seen another brand.

 

I use berryman carb. dip cleaner....Its does the job in 4 hours........Been using it 30 years...