Engine wont STAY running ??

[Mclovin]

Got a 2000 Honda 400EX stock engine..
Starts up fine.. idles smooth.. will idle forever it seems.. but once i start reving it.. its like the engine just seizes ! its shuts up instantly and wont fire. cranks over VERY slow like a dead battery but battery has a full charge.. then once it cools down it'll fire right back up and idle.. Im at a loss.. figured id give this a shot before i take it into a shop..

[Yetti]

sounds like to much to quick, fuel I mean. Has the float level been messed with on that lately? sucking in way to much fuel at once would cause what your seeing.

[Yetti]

http://www.exriders.com/vbb/forumdis...?s=&forumid=64

check the link, its EX riders 400 section (12,000 posts on tech there)

[95geo]

i'd start by cleaning the carb, then move on to jetting. could be a valvetrain problem though.

[Mclovin]

well i fired it up again tonight and im hearing what sounds like a bad bearing.. It was running GREAT up until a couple months ago when it quit on me at the sand dunes.. since then its been sitting waiting to get the wirring harness back.. now it does this crap.. I think it may be time for a total tear down.. maybe ill give the carb bowl a couple wacks and see if the float is stuck..

[Mclovin]

well i think the float was stuck.. started it up and being very irritated at this point i pegged it wide open to make it stay runnin kept stumbling and trying to die finally cleaned up and ran smooth and has been ever since. im thinkin it either came unstuck (float) or it got loaded up VERY badly when i was testing the new starter (cranking long periods without actually starting it) either way it runs good now.. but has some horrible knocking/rattling noise coming from engine (sounds like crank case)

[Big Daddy Rubicon]

Check your pilot jet, as for the knocking sounds like the cam chain?

[unclebeaner]

mine went bad on my 400ex. it makes a horible noise. pull the ten. and see if it still rachets out. mine fell apart.

[Motor Slut]

Check your cam and timing, Since it was at the dunes I would pull your air filter and check for sand. Sand in the motor is an instant death.

[Mclovin]

Originally Posted by unclebeaner

mine went bad on my 400ex. it makes a horible noise. pull the ten. and see if it still rachets out. mine fell apart.

whats a ten ?? and see if what ratchets out ?

[junk90xj]

tensioner.

[unclebeaner]

sorry. ya if the tensioner is bad the guide will make a bunch of noise and if it jumped time it might explain your running rough problem

[Mclovin]

Originally Posted by unclebeaner

sorry. ya if the tensioner is bad the guide will make a bunch of noise and if it jumped time it might explain your running rough problem

its not running rough.. its runs great now.. just makes some noise..

[Big Daddy Rubicon]

Originally Posted by Muddinguy

its not running rough.. its runs great now.. just makes some noise..

Still could be the tensioner that making some noise.

[unclebeaner]

Originally Posted by Big Daddy Rubicon

Still could be the tensioner that making some noise.

because the chain would be smacking around

[Mclovin]

Originally Posted by unclebeaner

because the chain would be smacking around

yea well i was running it around the block tonight and that chain said F YOU BUDDy ( i think) its not running now.. and it was made a nice rattling grinding noise before it quit and when it did the starter wouldnt crank it over.. havnt gotten into it at all yet

[unclebeaner]

chain might of broke and smacked the valves.

take off the cam cover and see if the cam has a chain on it and does it roll over. if i had to bet id say the chain or a valve was breaking and finally went snap hard to say without seeing it.