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400ex

  1. Performance Modifications
    I only trail ride and I’m looking to get a little more juice out of the 400ex on a bit of a budget, I was thinking of leaving it a stock bore, I have a big gun eco r slip on, and stock everything else, I was thinking of throwing a new stock bore piston in it just to freshen it up for the season...
  2. ATV General Discussion
    I picked up a 2001 400ex a while ago and I was told it was completely stock, I put a big gun muffler on it and rejetted it. Recently it started to burn some oil so I decided to take it apart to rebuild it and I found out it had a Webcam 450/451 cam in it and everything else is stock I was...
  3. Honda TRX
    Hello all. New person here. I have a 2008 400ex that I recently put an hmf slip on exhaust on along with a uni air filter and removed the airbox lid and snorkel. Hmf recommended a 42 pilot jet and 175-180 main jet with this set up. After installing a 42 pilot and 180 main I adjusted the mixture...
  4. Repair & Maintenance
    My husband and I have 400ex that we bought a few months ago and it wants to bog down whenever you go to get on the throttle. It idles fine, he has replaced the Jets, then bought a new carburator all together, CDI Box, coils, all he can think of, and it still doing the same thing. It runs fine...
  5. Repair & Maintenance
    Just wandering if the ignition switch from a 300ex will hook up to a 400ex?
  6. Repair & Maintenance
    It’s an 2002 trx 400ex Been bored to 440. Has hmf exhaust it will crank but won’t run. U have to give it 1/4 throttle for it to run but then it’s loud and the timing is right every single time. I’ve changed ever electrical part cam new battery changed the fly wheel took the head off checked the...
  7. Repair & Maintenance
    The gasket kits are different due to reverse components, I get, but are the crankcase covers any different? For example, will a 2002 right and left side cover fit on a 2007 crankcase? Will only the left cover work? What are the differences between motor components between these two groups of...
  8. Repair & Maintenance
    Hi guys I have a 2006 400ex. I’m doing a clutch replacement, and it’s never once been opened up. I have tried everything from hitting it with an impact hammer to a crow bar on the fin, and nothing will take it out. The cover is just stuck. Can I have some help with what to do? Thankyou guys!
  9. Repair & Maintenance
    ok so basically at first machine did this thing were jut would run and just quit and quit but what we didn’t know is that it want getting oil so it pretty much blew it up and i got a brand new top end professionally done so it was done right and i brought it home and it’s kind of doing the same...
  10. 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...
  11. 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...
  12. 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...
  13. 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...
  14. 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...
  15. 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...
  16. 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...
  17. 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...
  18. 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...
  19. 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...
  20. ATV General Discussion
    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...
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