400ex problems 

Hey guys thanks for the support and info!!! I will be doing a video when I get the bike back. Come to find out the guy who had it before me didn’t put the carb back together right and a few key pieces were missing inside the carb itself. So once I get it back I’ll do an update video

The float is plastic so it can't be bent like metal, but I just heated mine up and bent the plastic a bit to allow the needle to be open a little more. It's a jank fix but it worked for me super well

Valve cover gasket definitely wouldn't cause that he has to lean jetting it needs to go bigger and it will fix it or try moving the slide needle clip down on the needle so the needle doesn't sit as low and that is the stock head pipe it's just a yoshi slip on I have a couple of the same exact head pipes sitting on my shelf from when I changed both of my 04 400exs exhausts you need to go up a size or two on the pilot jet and it will probably fix the issue .. make sure the air fuel mixture screw it turned out 2 1/2 turns that's the typical sweet spot for it on almost any at or dirt bike .. but I would also get a rebuild for the carb that way your sure there isn't any dirt or scum in the carb .. buy a set of torch tip cleaners they are super small sizes and they fit perfectly inside the jets to clean them out a little and if your good enough you can even enlarge the jet with them they are little round files that come in a set they are super cheap

mine came with a 150 with pipe.. clean carb. thats a LEAN bog with slip on pipe put 42 secondary and 175 to 180 main and airbox lid OFF. ik that sounds rich. mine runs like a raped ape. and my kx450 runs a 170 main. and thats LEAN with the full pipe it has on it. if your trying to find a airleak start the bike have it idle and get starter fluid and spray around the airboots... if the rev pics up you have a airleak there. if it stays the same no leak. lean bogs sound hollow. like the engine sounds like its just pumping air. rich bogs sound deep and like the engine is strugging to run

On some there are different slots on the carb needle and you can adjust how fast it let's fuel in, that was the problem on mine

42 pilot, 180 main jet, 2 turns out if you're at 1000ft elevation or less. 3rd clip position from the top of the needle, take snorkle and air box lid off. Will run perfect.

Drop in a bigger Pilot jet, try a size 40 Pilot jet with that pipe. Changing the Main jet is NOT going to do a thing on the idle circurt hints rough or no idle. Clean the carb completly and check your intake boot for leaks/cracks it could be sucking in air leaning out the engine. The Pilot jet controls idle to about 1/4 throttle, the needle controls 1/4 top about 3/4 and the main jet controls 3/4 to Full throttle.

The guy in another video moved up a notch on the throttle needle and it fixed the idle problem. The throttle needle has 4 notches.

New motor. That's what I had to do to mines, it's not worth going on the top. It's only a matter of time before it stops running

What ended up being the problem? To big of jets?

If you haven't figured it out it could be the air screw or like you said valve cover gasket

That same bolt u point at, my motor blew and start leaking oil out of that side only

Check your Needle valve setting. Go back to Stock and try again. If she is running well on full choke then stalls of ckoke it means that you are getting overfueled on idle It was named a choke for s reason If we are choked of "AIR" then we would suffercate and die. Your mixture is messed up go back to factory settings on all carb settings including the needle.

I will be doing an update video here soon. Found the problem and once I get the carb back and installed I will update everyone thanks for all the comments you guys helped me figure out the problem!!!

Deff carb issue air filter clean i would hope. And valve cover gasket wouldnt cause this issue . Carb could use a rebuild i would say

Can any body help out I have a trx250 2002 sportraxs and when the chokes off it won't rev up and tries to dies with choke it cuts out and full rev with too much gas I have mess with the air Mistral idle srew at the bottom of the carb I don't know what the problem is before it had that problem after pinning it down the road it would die out unless you put on the choke

Figure it out?

Your giving it full choke when it cuts off your not shutting the choke off .. you need to push it twords the front of the bike to shut it off .. I’m having the same issue but it’s because of fuel mixture screw your bikes running lean I believe .. because it runs better with the choke half way but not fully open = too much air cuts the bike out ... that’s what I’m getting from trial and error trying to tune my 400

With my pipe I run a 157 and it runs amazingly

If anybody has input, I need some. Ive got a 99 Trx400ex. I just did a top end rebuild, new valves, wiseco 10:1 piston, stage 2 hotfcams, HMF slip on. I don't think its running lean, but it keeps backfiring on Decel, or when I shift. It pops / backfires. I don't think its running lean. It starts with no choke, idles fine. What could this be?

Turn up the idle I bet it’s idling to low

You still got the 400? Im looking for another one to buy and want a honda. I have a suzuki ltz 400 with 440 kit cams pp head.i buy your 400

Bro there's a screw under your carburetor that controls your air fuel mixture try messing with that I had the same problem and that's what it was

Theirs a needle jet that’s at the bottom of the carb try messing with that

Bigger jet

Plugged pilot sircit

Hey everyone, My 400ex turns off when it gets warm. I leave it off for about 5 mins then runs fine for another 20-30 mins then turns off again. Any ideas? Thanks in advance.

Any update?

I only ride without choke

It getting too much gas.its getting flooded

Your fully choking it .....!!! When you say it runs good full choke that’s really the off position it’s confusing because of the arrow

Intake leak

160 jet

2 years no one was going to tell this pore guy he’s fully choking the bike 🤦

You should not even be considering riding it on half choke it must be fixed.

That is a full system pipe not a slip on

Too lean bc the stock jet is a 142 so try a 160