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  1. 08 400ex will crank but won’t turn over

    Repair & Maintenance
    I was riding my quad one day running perfectly no problem. I put it away and no problem at all the next day I go start it up it sounds normal but 1 minute into it warming up it just dies. Well I start it up again and lay a little on the throttle and keep it in one spot and the rpms go down and...
  2. 2000 trx400ex hits but will not start

    Repair & Maintenance
    Hey folks, I have a 2000 400ex that is on the verge of being pulled outside and burnt. Haha! Not really but it's bringing me joy currently to think about doing that. The quad originally had a cam sprocket bolt break and created shaving from the inside of the valve cover this clogging the filter...
  3. 400ex shuts of randomly

    Repair & Maintenance
    ok so i just replaced my head gaskets bc they were leaking and i started it up and it ran fantastic and then it shut off randomly and it wouldn’t start but eventually it did and i ran it again for a bit but then it shut off again and i took it home after that and it won’t start since and it has...
  4. 400ex won’t start

    Repair & Maintenance
    I’ve had my 400ex for about a year now, never had a problem until this spring when I went to get it out. It was low on oil so I put some in and went to start it. It wouldn’t start. It would fire and run at high rpm for 4 secs and then die out and that was if you worked the gas. First thing I...
  5. Changed 400ex head gasket and motor blew

    Repair & Maintenance
    Needed some thoughts I just changed the head gasket on my 2000 400ex and on my test drive just now the motor locked up and refuses to even turn over,the noise it made sounded liked the cam chain got loose or something. I'm new to this so this was my first go at taking a motor apart. I watched a...
  6. Help with 400ex weird problem!

    Repair & Maintenance
    Hey guys, any ideas would be greatly appreciated on this. So it started a few months ago, riding with some buddies and my 400ex all of a sudden lost power. Wouldn't fire, wouldn't sputter. Towed it home, and then it fired right up. It continued this pattern for a week or two, ran perfectly for...
  7. 400ex top engine mount wont line up

    Repair & Maintenance
    Bought this 400 that basically just needed the top end rebuilt. Guy started the project but never finished it. So i got to wrap up his project. I was trying to put the top engine mount in and I can not get it to line up. The head cover that he sold with the waud was broken right at the top...
  8. 2002 400ex throttle problems

    Honda TRX
    My 2002 trx400ex goes 1/2 throttle or 3/4 and then it bogs out. Sometimes it won’t even let my give it any throttle. I took the air box lid off and it helped so I put some holes in the lid. But it still did it after a little. Then I took the jets out and cleaned them. Could there be an...
  9. 2002 Trx400ex cutting out and dying

    Honda TRX
    I bought a 2002 400ex a few weeks ago and it will idle fine and as long as you don’t lay into the throttle too hard then you can shift through all the gears. When I hammer the throttle I can make it to about 2nd gear and then it cuts out and dies, it also has a little difficulty starting back up...
  10. 2003 Honda 400ex

    Honda TRX
    Recently bought a 400ex.. battery was zip tied to the battery cage.. went on a rough ride and felt the battery dangling by my leg, ground cable had broken off and once I put it back with the broken peice it didn’t crank no more.. but once I jump the start solenoid it cranks on but my electric...
  11. 02 400ex won’t start popping/backfiring

    Community Help
    Hello new to the forum and new to the Hondas sorry if I posted this in the wrong place but I need help, I recently purchased a 2002 400ex of a guy that could not get it to run. Currently it will only start when throttle is half open and it pops/backfires like crazy I trued full throttle one time...
  12. 400ex makes grinding sound then turns off

    Repair & Maintenance
    Ok so I just bought a 1999 400ex and it ran pretty good and then all the sudden I was riding it like locked down or somthing and I put it in the garage and it had other problems with spark and stuff so eventually I replaced all the wiring on it with a whole new wiring harness and everything and...
  13. 400ex makes a grinding noise after running

    Honda TRX
    Ok so I just bought a 1999 400ex and it ran pretty good and then all the sudden I was riding it like locked down or somthing and I put it in the garage and it had other problems with spark and stuff so eventually I replaced all the wiring on it with a whole new wiring harness and everything and...
  14. 400ex frame

    Repair & Maintenance
    Hey guys, I need a new frame for my 05 400ex. I have a friend who will give me a frame for an 01 400ex. Will my engine and stuff fit inside this older model frame?
  15. Need New Frame

    Repair & Maintenance
    Hey guys, I recently bent up the front of my 2005 trx400ex does anyone have a frame around or near Connecticut that they would sell me, if not does anyone know where i can get one for a good price?
  16. New to this site.. couple of questions

    New Member Introductions
    Hey, I just bought a 2005 400ex and am new to this site. I bought it with a brand new engine in it. I have a few questions about it. What is the best oil to run in it and is full synthetic ok for it or not? Also when its running it makes a small clicking sound coming from the engine, and im...
  17. Day at the Track

    ATV Media
    YouTube - Trx 400ex and 450r jumps
  18. Manual for 400ex trx

    ATV General Discussion
    Where can I find a manual online either pdf form or something. I'm trying to run wires, and trying to figure why the quad won't run.... thanks
  19. FS: 2001 400EX Parts

    ATV Parts for Sale
    Email with request and offer - entire bike going, plus extra parts. Local Pickup or shipping available with payment. Thanks guys!
  20. 300ex jetting(not quite right)

    Performance Modifications
    Alright i got my 300ex going a running good finally and i figured i would have to rejet so my brother had the stock jet out of his 400ex a 148 so just for kicks i put it in just to see how far off it would be. I did a plug check and its not far off. I have good throttle response good when i...