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Thread: 400EX Won't Start

  1. #21
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    My advance auto said they didn't loan compression testers. So I'll try the trick with the gas or starter fluid in the spark plug hole first. If I get combustion, I can assume it's still got decent compression and dive into checking the timing. I'll keep everybody posted.

  2. #22
    Join Date
    Dec 2010
    Location
    Indiana
    Posts
    917
    Quote Originally Posted by MoparManiac117 View Post
    My advance auto said they didn't loan compression testers. So I'll try the trick with the gas or starter fluid in the spark plug hole first. If I get combustion, I can assume it's still got decent compression and dive into checking the timing. I'll keep everybody posted.

    If you have good spark and it wants to fire, but won't run then these problems could be the reason..

    improper choke operation

    incorrect adjusted carb

    leaking carb insulator

    improper ignition timing, faulty ICM or ignition pulse generator

    contaminated fuel.......like water, moisture in fuel.

    Also if you have spark, but it won't start and your plug is wet with gas.....

    flooded carb

    throttle valve open

    dirty air cleaner (you need air so if you got a mouse nest in there from the barn.....)

    improper adjusted pilot screw
    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. #23
    Join Date
    Sep 2012
    Posts
    177
    Quote Originally Posted by DragonGunner View Post
    If you have good spark and it wants to fire, but won't run then these problems could be the reason..

    improper choke operation

    incorrect adjusted carb

    leaking carb insulator

    improper ignition timing, faulty ICM or ignition pulse generator

    contaminated fuel.......like water, moisture in fuel.

    Also if you have spark, but it won't start and your plug is wet with gas.....

    flooded carb

    throttle valve open

    dirty air cleaner (you need air so if you got a mouse nest in there from the barn.....)

    improper adjusted pilot screw
    Those are all a possibility. But it doesn't make sense that those would just happen in the middle of riding. Given the problem with cam chains on 400ex that would be the next thing to check.
    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

  4. #24
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    I think we're getting closer to the timing being the culprit. On the chance that maybe the battery wasn't making full spark, I hooked a jumper box up to it. No differene. Then I took the plug out, sprayed some starter fluid in the cylinder, put the plug back in and left the jumper box hooked up while I tried to start it. Still nothing. Didn't even make an attempt at starting. The starter just sounds like it's free spinning. I have an '07 400 I keep parked right behind his. Just for a comparison I fired mine up. The starter sounds like it's trying much harder to turn the engine over. I guess checking the timing is the next thing in the list

  5. #25
    Join Date
    Sep 2012
    Posts
    177
    Given how it sounds I would be willing to be it is a snapped timing chain
    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. #26
    Join Date
    Mar 2009
    Location
    Central NJ
    Posts
    84
    It could be the cam decompression, If it sounds like it wants to start when you keep pumping the throttle then that's your problem. I had that happen to my 400EX.
    87 TRX310R
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    00 TRX416EX

  7. #27
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    Quote Originally Posted by Drifterboy3 View Post
    Given how it sounds I would be willing to be it is a snapped timing chain
    If the chain was snapped, I would think the valves wouldn't move. They're moving in the head, so it could be just out of time. I'm curious about the valve clearance though. Once I dig my feeler gauges out, I'm going to check that before I pull the valve cover off.

  8. #28
    Join Date
    Sep 2012
    Posts
    177
    Your correct they would not move. I didn't know you ever pulled the valve cover plugs
    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

  9. #29
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    Quote Originally Posted by Drifterboy3 View Post
    Your correct they would not move. I didn't know you ever pulled the valve cover plugs
    I just pulled the lash inspection covers to make sure I was getting valve movement. Once I find my feeler gauges, I'll check the clearance and then pull the valve cover and check the timing. I think it's in the valve train.

  10. #30
    Join Date
    Sep 2012
    Posts
    177
    We'll make sure you set the engine to TDC before you pull the valve cover. Otherwise you can strip bolts in the head.
    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

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