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  1. 2003 Honda 400ex decompressor

    Maintenance / Important Information
    Hi every one, I just bought a 2003 400EX bored to 426 and notice that it’s missing the decompressor lobe on the camshaft. I was wandering if it would still start or I need to buy the lobe. Thanks in advance!! Also, what main jet should I be running? The engine is bored to 426 like I said, it got...
  2. 400ex neutral light won’t turn off?!

    I have a 2002 400ex and my neutral light never worked. Until one day I bought a new Oem neutral switch and wire going to it. I also put some never-seize on the bulb because it had loose connections. Now the neutral light will stay on in every gear and I can’t figure out why. If anyone knows...
  3. 400ex jetting and airflow

    TRX General Discussions
    I have a 400ex bored to 416 and have a stage 2 hotcam. I have a krome dg slip on exhaust without spark arrester. Stock intake and carb with foam filter. I was wondering if I should change my jets, and if so what to? If I should make more airflow through the intake box with holes? It runs good to...
  4. HELP!!! 2005 trx400ex with loud ticking noise

    Maintenance / Important Information
    Hi i have a 2005 honda trx400ex with a loud ticking noise. i did a valve adjustment and problem was still there. any advice on what to look at next. the motor is completely stock. i have done some research and found it could be different things causing the ticking. how am i able to tell if my...
  5. 400EX Issue with Aerated Oil - Running Hot

    Hi there, I'm trying to run down a problem with aerated oil and I'm running out of things to check. Any advice would be appreciated. First question: This can't be normal right? After warming up the bike for 5-10 minutes, shut it off, check the dip stick or drain the oil from the oil tank...
  6. 400ex enough adjustment in carb means no need for jetting?

    Hi, I have a 100% stock 2002 400ex, I still have the stock exaust and no plan or money to get an aftermarket slip on. The other day I took the tip of the muffler, and I really liked the way it sounded, it was a lot deeper then stock, and sounded great under a load. My question is, i rode it...
  7. engine wont stay running after rebuild on 2007 400ex

    rebuilt the top end on my 2007 honda trx400ex recently because it was blowing a little smoke and now it wont idle at all I turned the idle adjustment screw all the way in and it still will not idle it will idle if the it is choked but not when the choke is off.
  8. 2003 400ex pop sound only in 1st gear

    2003 400ex FOX Podium shocks Yoshimura full exhaust K&N filter DynoJet Stage 2 Jetted ProTaper handlebars ProTaper grips I have a pop sound only in 1st gear. Chain has 1 1/2 play in it. Any suggestions?
  9. 400ex tuning problems

    I need opinions on my tuning: I've got a 2000 400ex, original motor, wrapped header, oil change. Rebuilt the carb and adjusted valves. After a lot of trouble with backfiring through the carb (signifying really lean) I'm running a 42 pilot jet and a 150 main jet. This helped a lot, but I'm still...
  10. Jetting in Colorado

    Dyno/Tuning Room
    I know that there is a million different threads on this. However each set up is different. When I purchased my quad I was in TN and now I reside in Colorado. My quad seized up on me since I have been here. I have since rebuilt it and now I am in need of information on jetting for my altitude. I...
  11. Green Wire Mod?????

    Has anyone ever tried this mod? does it actually work? is it worth it? will it work on a 06' 400ex?
  12. Somebody please help before i throw my 400 out the window

    TRX General Discussions
    My 02 400ex has nothing aftermarket besides a big gun es exhaust just the slip on. I recently got my 400 back from the shop it sat for months there not started it wont start i cleaned the carb and set the jets to normal settings first if someone can get me all the jet specs like how many turns...
  13. 400ex safety switch problem

    Site Issues, Bug Reports & Suggestions
    I have a 02 400ex and my safety switch by the shifter broke and i have no ignition or lights. Ive connected the 2 clutch lever wires together and still nothing. Is there a way i can bypass this or no
  14. !!!!!! Used 400ex atv tires for sale !!!!!!!

    For Sale
    I've got a full set of used tires for sale! TIRES:* FRONT TIRE (FULL SPEC) 2 x Ohtsu® 22 X 7-10 REAR TIRE (FULL SPEC) 2 × ITP HOLESHOTS 20 X 11-9 These still have 40% tread available. Pick up only! Northwest Georgia. I have pictures available.... Call or text 678-770-2518 Chris $100.00 or best...
  15. 400EX Setup/Repair

    TRX General Discussions
    Hey all, just recently got an 07 TRX400EX. Nice quad, but needs some work. Figure this is a good place for me to get some help! Things the quad needs: 1.) Brake light works fine when motor is off. Once motor is on, brake light flickers at best -- mostly doesn't work. 2.) Suspension sits way...
  16. 400ex high compression piston

    I'm going to be rebuilding my 400ex I want to put the highest compression piston possible in it and the largest diameter possible. what brand and where do I get it?
  17. 400ex top end rebuild

    I just rebuilt the top end on my 400 ex. Was burning lots of oil. It had white brothers exaust and k&N air filter, 38 pilot and 160 main jet. I bored the bike .20 over and put in a high comp 11.1 wiseco piston. I also put in stage 2 hotcams. Now, I already changed my main jet to a 172 which...
  18. Trx 400 Carb Problem?

    I have an 05 Trx 400ex i bought off craigslist The only issue are the back breaks (currently bleeding them) and the carb leaking. To the right of the yellow choke, and hose, you can see a small nozzle. There is a tube that is long enough to fit around the nozzle shown here This tube leads...
  19. 2002 400ex dies full throttle

    I just bought a 2002 400ex off a guy on Craigslist. I have only drove the quad around a little, seems to be fine. But today I took it down the road full throttle, and at top speed, I pulled in the clutch and stoped giving it gas and it dies. So once I stop, I start it up again, and runs fine...
  20. 400ex low compression

    TRX General Discussions
    I just bought a 2002 400ex for $1450. It started, idled fine with choke to start it. Then it idled fine after. I let it warm up, then shut off the gas. I plugged the compression gauge in and put it full throttle, then let it crank. It only showed 90psi. So it's low. But it starts easy and no...