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Thread: 400EX Won't Start

  1. #11
    Join Date
    Jan 2012
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    Iowa
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    Advance auto or autozone rents compression test kits orielys sp? does as well I think. Under the 'loaner tool' program.

  2. #12
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    Jan 2012
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    You could also pull the valve cover and check the cam chain and tensioner. But that's all ballpark from my end, I don't know too much to help ya other than the above rent a tool help lol. Try and see if you can get it to start on brake cleaner and idle for a couple seconds. It will burn clean and wont harm anything. Other chemicals have oily residue and will make it stumble and or not pop off. Good luck, Wish I could offer more help

  3. #13
    Join Date
    Sep 2012
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    177
    You may be able to rent a tester from an auto store. BUT it's not the same thread size for a quad and car so that is worthless. Of it's low on compression my bet would be either valves are slightly out of spec. Or your cam could have skipped a tooth on the chain. (I don't know how it happens bit it happened to my cousin on his yfz)
    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. #14
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    They come with different adapters and the fact NGK is one of the worlds top oem spark plug maker auto and bike/quad/sled/boat/anything that takes a plug, NGK makes it run flawless. Plus Honda cars would take a similar plug so the thread pitch adapter would be included. Can always call and ask, Beat buying one just to 'test'.

  5. #15
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    Dec 2010
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    Indiana
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    Quote Originally Posted by MoparManiac117 View Post
    It has spark. I put the plug in the boot and touched the electrode to the header. Hit the starter and it was sparking. I put the plug back in and tried to turn it over quite a few times while punching the throttle. Pulled the plug back out. It was hard to tell if it was wet or not where I had anti seized the threads. Should it have been noticeably wet with gas? Either way, I went ahead and took the carb off. Just out of curiosity I left the throttle cable attached and took it to full throttle a couple of times. It squirted gas out of the engine side. So that should mean it's getting fuel, right? What should I check now?

    The plug where you gap it should be wet with gas.....sounds like its getting from carb, but we don't know if its getting to the cylinder.....you said it quit while it was running....try a little gas down the plug hole, put plug back in and see if it fires. If doesn't fire a low compression reading could be several things. Also how good is your battery....a weak battery well spark a plug but may not be enough, if you got a charger try and boost it while starting.....however a weak battery would not of made it quit running while he was riding.
    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

  6. #16
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    Quote Originally Posted by Drifterboy3 View Post
    You may be able to rent a tester from an auto store. BUT it's not the same thread size for a quad and car so that is worthless. Of it's low on compression my bet would be either valves are slightly out of spec. Or your cam could have skipped a tooth on the chain. (I don't know how it happens bit it happened to my cousin on his yfz)
    If gas and spark are good the timing is the next thing I would check too.
    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

  7. #17
    Join Date
    Sep 2012
    Posts
    177
    If you can't or don't want to buy or rent a compression tester you can go straight to pulling the valve cover. It's pretty straight forward and can be done with basic hand tools and common sense

  8. #18
    Join Date
    May 2013
    Location
    Central KY
    Posts
    31
    The compression tester from autozone wasn't the right thread size and didn't have an adaptor to go down to the needed 12mm. I'll try putting a little gas in the cylinder and see if it fires. I'll pull the valve cover and check timing too. Battery was just taken off the charger because they killed it trying to refire it when it died. They had to push it up the hill I get it back in the barn anyway.

  9. #19
    Join Date
    May 2008
    Location
    North Carolina
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    2,158
    Go to advance auto... they have one.

    Could just be a plugged pilot jet though. Might be what killed it and why it won't start back if it is trying to start at all.

    If not, cam chain or compression.
    '08 Monster Kawasaki KFX450R (black)
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    '99 Sport 400
    Out of a time capsule
    Bone stock, new condition (6/08)

    '00 TRX400EX
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  10. #20
    Join Date
    Sep 2012
    Posts
    177
    One thing before you pull the cover. Pull the plug and put one finger over the hole and turn it over. Of you have decent compression it will push your finger (from the air preasure)
    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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