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Thread: 400EX Won't Start

  1. #31
    Join Date
    May 2007
    Location
    Wayland, MO
    Posts
    2,316
    I have the same problem with a friends 300ex that he brought me to fix. It's getting everything it needs, spark, air, fuel is getting in and out of the carb., valves are in spec, has good compression, new plug, fresh gas, wiring is good, kill switch isn't on. Damn thing still wont start for ****. Some how the carb is getting fuel into it and out of it, the valves are opening and closing yet fuel isn't getting into the cylinder. I took it to a friends to see if he can find out what's wrong with it. I ran out of ideas, other than ether, but that wouldn't help the main problem.
    2002 Ford Ranger (Red, Westin Brush Guard, K&N CAI, Clearance Lights, couple other little things)
    2012 RAM Power Wagon (Black, Line X, Weathertech, Cover King, Flowmaster, Tinted, DiabloSport Trinity, Rertro Shop Custom Headlights, Leveled)
    2006 450R (MX/Dune/QFMX Machine)
    2005 407EX (XC, GNCC, Harescramble Machine, Not much left that's stock, PICS)

    R.I.P. Caleb Moore, you will not be forgotten.
    R.I.P. Tyler Saxton, I'll never forget you bud.

  2. #32
    Join Date
    Dec 2010
    Location
    Indiana
    Posts
    1,040
    Quote Originally Posted by Stickman400 View Post
    I have the same problem with a friends 300ex that he brought me to fix. It's getting everything it needs, spark, air, fuel is getting in and out of the carb., valves are in spec, has good compression, new plug, fresh gas, wiring is good, kill switch isn't on. Damn thing still wont start for ****. Some how the carb is getting fuel into it and out of it, the valves are opening and closing yet fuel isn't getting into the cylinder. I took it to a friends to see if he can find out what's wrong with it. I ran out of ideas, other than ether, but that wouldn't help the main problem.

    Maybe really low compression....takes compression to suck the air and fuel in.....
    1984 Honda 200M ATC
    1985 Honda 200X ATC
    1986 Honda 200X ATC
    1999 Honda 406EX....11:1, Web Cam / Hardened rockers. Ported. WB CDI. CT Racing header. WB E-Series slip on. Lonestar swinger.
    2001 Honda/KTM 520 Hybrid Quad. Its like a 400EX but twice the horsepower.
    2014 Artic Cat Wildcat Trail XT

  3. #33
    Join Date
    May 2007
    Location
    Wayland, MO
    Posts
    2,316
    Yea, I didn't check it with a tool but it seemed like it had decent compression when I stuck my finger in the spark plug hole, but I guess I wouldn't really have anything to compare it to. My friends going to see if it will fire or run with ether, then go from there. My friend that brought it to me said the guy he bought it from hit a water hole and it died and wouldn't get started again. They managed to pull start it in 3rd gear and it ran for a couple seconds and died, hasn't started since. That makes me think a wet connector or something electrical. Anyway I don't wanna thread jack, but thanks for commenting Dragon!
    2002 Ford Ranger (Red, Westin Brush Guard, K&N CAI, Clearance Lights, couple other little things)
    2012 RAM Power Wagon (Black, Line X, Weathertech, Cover King, Flowmaster, Tinted, DiabloSport Trinity, Rertro Shop Custom Headlights, Leveled)
    2006 450R (MX/Dune/QFMX Machine)
    2005 407EX (XC, GNCC, Harescramble Machine, Not much left that's stock, PICS)

    R.I.P. Caleb Moore, you will not be forgotten.
    R.I.P. Tyler Saxton, I'll never forget you bud.

  4. #34
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    So I finally got time to check the valve clearance. There was none on any of the valves. So I adjusted them to the proper clearance. Tried again and still nothing. Guess it's time for the head to come off. Would the fact that there was zero valve clearance give any clue as to what's wrong? I'm getting low on patience and time (I have race season starting in about a month). Again, advice is appreciated.

  5. #35
    Join Date
    Sep 2012
    Posts
    177
    Check the timing before you pull the head.

    Set engine to TDC
    Remove valve cover
    Remove upper engine plug.
    There is a "T" marked on the flywheel and should line up with the notch in the case.
    There check on the cam. There are two - - marks that should line up parallel with the side of the head.

    If it still doesn't fire after that I'm out of idea. It wasn't smoking before it quit was it?
    2003 400ex
    powermadd star series handguards w/wrap-powermadd gauntlets-elka stage 3 front shock-tusk nerfs- 11:1 piston-full fmf-gtt xc link-oury grips-909 bars-precision anti-vibe clamp-K&N filter-ccp steering stabalizer-oversized oil tank

  6. #36
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    Yeah. After I check the timing, if it's right and it still doesn't fire, I taking it to a shop.

  7. #37
    Join Date
    Sep 2012
    Posts
    177
    Get back to us!
    2003 400ex
    powermadd star series handguards w/wrap-powermadd gauntlets-elka stage 3 front shock-tusk nerfs- 11:1 piston-full fmf-gtt xc link-oury grips-909 bars-precision anti-vibe clamp-K&N filter-ccp steering stabalizer-oversized oil tank

  8. #38
    Join Date
    Jan 2012
    Location
    Iowa
    Posts
    657
    Did you ever try and swap another CDI box on it and try to fire it? Shot in the dark and free if you have a friend with a 400 too.

  9. #39
    Join Date
    Dec 2010
    Location
    Indiana
    Posts
    1,040
    Quote Originally Posted by MoparManiac117 View Post
    So I finally got time to check the valve clearance. There was none on any of the valves. So I adjusted them to the proper clearance. Tried again and still nothing. Guess it's time for the head to come off. Would the fact that there was zero valve clearance give any clue as to what's wrong? I'm getting low on patience and time (I have race season starting in about a month). Again, advice is appreciated.
    You made sure it was TDC when you checked the valves right?
    1984 Honda 200M ATC
    1985 Honda 200X ATC
    1986 Honda 200X ATC
    1999 Honda 406EX....11:1, Web Cam / Hardened rockers. Ported. WB CDI. CT Racing header. WB E-Series slip on. Lonestar swinger.
    2001 Honda/KTM 520 Hybrid Quad. Its like a 400EX but twice the horsepower.
    2014 Artic Cat Wildcat Trail XT

  10. #40
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    Yeah. The 'T' was centered up in the small inspection hole on the left crankcase cover. Engine rotated counterclockwise to get there.

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