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I have an 02 400ex, it has mods but I dont really know exactly what. I was told it had a 440 kit, jets and a few other things. It has DG exhaust. Anyways it doesn't run right, if you open it up it falls on its face, spits and sputters. Does this have something to do with the carb? If so should i rebuild the carb or buy a referbished one for $95? Also it burns oil pretty bad, piston rings? thanks matt
 

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I have an 02 400ex, it has mods but I dont really know exactly what. I was told it had a 440 kit, jets and a few other things. It has DG exhaust. Anyways it doesn't run right, if you open it up it falls on its face, spits and sputters. Does this have something to do with the carb? If so should i rebuild the carb or buy a referbished one for $95? Also it burns oil pretty bad, piston rings? thanks matt
yep..burning oil..means it needs new rings..for the carb..before you waste your money on a new carb..take that one off..and give it a good cleaning..clean your jets out real good..some carb spray cleaner...one wire from a wire brush..nothing bigger !!..take the carb off..take the intake o-ring off..< carb cleaner makes the o-ring swell >..take all the jets apart..clean the inside out of the jets with the carb cleaner and wire from the wire brush...don't force the wire through..or it might break off inside the jet..which means you will need to buy a new one..lol..clean the carb bowl out..take the float off the carb..spray the float needle real good..wipe it off..careful not to scratch the float needle..or it won't seat right..clean everything real good..blow the carb out with some compressed air if you have a air compresser.put it all back together..see how it runs.
 

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sounds like the carb.maybe not jetted right.only way i know to tell if it has a 440 kit is take the topend off and measure.
 

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Ok i will take the carb off and clean it all out and let ya know if it works. Ok so how do i figure out if it has a 440 kit or not? Sorry dont know much about small engines.
 

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Good chance its all of the above and then some! Before you do carb work check the engine compression and ,if your able to, do a leak down check. Likely one or both will read bad. Assume you will need a valve job aswell as rings if the readings are bad. If your burning oil its possible motor was run with low oil level at some point which is very hard on an engine especially the top end. Ive worked on a couple of motors that ran like yours that ended up wearing the lobes off the cams due to the lack of lubrication.
Once your sure you have a good motor, make sure your exhaust is sealed properly...You have a DG? Make sure the packing is good in the muffler if so equipt. On the intake side of the motor you need to make sure you have a good clean air filter because a dirty one will choke your motor. You also need to make sure you have a good tight seal from the air box all the way to the motor.
Dont know about yours but some motors that are heavily modified have issues with the rev limiter...just something you might want to look into sometime.
Seems like there was something else I wanted to say but cant remember...Oh well...Hope I was of some help
 

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at a stealership you will always pay to much the people on here will tell you all you need to know they have a lot of knowlege
 

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at a stealership you will always pay to much the people on here will tell you all you need to know they have a lot of knowlege
LOL yea thats what i figured. Its that way at any type of dealer
The money you thought you might spend on a carb would pay for a honda service manual with a little left over and you can down load them onto your cumputer nowadays for just a few dollars. A honda service manual is a very easy manual to read...they practically take you by the hand and lead you through all the steps. Give it a try...might not be as difficult as you may think
 

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There's a free downloadable manual for a 400EX at this site.

maxmekker.com
 
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