400ex wont stay running!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!

[jak1389]

hey guys, need some quick help. to make a logn story short i need to take apart the motor. now i just finished putting it back together and, it starts, but doesnt idle or stay running, and backfires. well, i clean the carb to make sure the pilot jet wasnt blocked, and it is still doing the same thing. i am guessing it may possibly be the timing. now, with timing it does it matter if the lobes are facing up or down when at tdc? please give me any suggestions you may have. thanks



~jason

[yamablaster24]

just like went through same thing. I assume i had the timing wrong but never put motor back together.

[yamablaster24]

Lobes are facing down on compression stroke. Line up the T and have the three lines perfectly parralllel

[jak1389]

checked my timing and everything is perfect. not sure what it may be. i am BAMBOOZLED!!

[jak1389]

any ideas? i am going to dissasemble the entire carb tonight and clean the crap out of it with gum out. if you have any ideas or suggestions, i would very much appreciate it.

[stumpleg]

you might try messing with the idle screw

[blakefoote]

wut is the temperature around your house? b/c the 400exs do not run to well if it is too cold...that could be the problem

[jak1389]

yesterday it was around 50. i started it up on full choke, and it started right up and idled nicely and i gave it a lil gas and it seemed to be fine. so i let it warm up for a few, then put it on mid choke for a little bit. after i took off the choke it acted as if it wanted to die out, and everytime i gave it gas it backfired. i am as of now assuming it is a carb problem.

[Colby@C&DRacing]

if it runs fine with the chocke on I would say the pilot circuit is plugged.

[400exrider707]

Originally posted by Colby@C&DRacing
if it runs fine with the chocke on I would say the pilot circuit is plugged.

[jak1389]

now how do i clean the pilot circut? can i just take out my pilot and shoot a crap load of gum out down it, or what is the best route to clean that spot?

[jak1389]

also, would this account for it backfiring when i hit the throttle? it does this bad especially off choke.

[trxkruzoffman]

maybe its flooding out, try taking the carb off then blowing the s**t outa it with an air hose. my 400's carb is leaking somewere so it trys to flood when im riding it, it dies and wants to quit.

[jak1389]

ok everyone, welll a freind and i have cleaned the snot out of the carb many times, its soo clean you can eat of it. the carb is not the problem. i hav a small suspesion that it has a slight advance in timing. could it possibly be that i was running the automatic decompressor (plunger and spring) even though i shouldnt have. ever sicne i took it out like its supposed to be that it now needs it in the motor? any ideas would be greatly appreciated. thanks


~jason

[bullet3z]

Originally posted by trxkruzoffman
maybe its flooding out, try taking the carb off then blowing the s**t outa it with an air hose. my 400's carb is leaking somewere so it trys to flood when im riding it, it dies and wants to quit.

You need to check the float bowl, that might be your problem.

[400exrider707]

Originally posted by jak1389
ok everyone, welll a freind and i have cleaned the snot out of the carb many times, its soo clean you can eat of it. the carb is not the problem. i hav a small suspesion that it has a slight advance in timing. could it possibly be that i was running the automatic decompressor (plunger and spring) even though i shouldnt have. ever sicne i took it out like its supposed to be that it now needs it in the motor? any ideas would be greatly appreciated. thanks


~jason

Ok firstly, when it runs fine with full choke and then you take the choke off and it starts dieing, that is a lean condition. By running it on choke your are richening it up. Also what cam do you have in yoru quad now? Did you have the plunger and spring in with an aftermarket cam?

[400exrider33]

hey you might need to re jet. Also my buddy had a raptor and we experienced the exact same thing. We tore the carb apart umteen times and still it would backfire and want to die out. We finally got tired of it and took it to a shop. the guy said that there was a electrical that was back in the rev box area. That might be where you want to look. But i would say that jetting might be something to look into too:ermm:

[jak1389]

ok one more time, it is not the carb, the float is fine, i do not need to rejet, it was fine before and i had the same mods, i did adjust the needle considering the drastic weather change in climate.



yes i did run the plunger with the aftermarket cam i have, which is a hotcam stage 1. but i just found out i was 1 tooth off with the timing. i am guessing that was the problem. i will probably let everyone know later tonight.

[EXrobash]

mine did the same thing...i turned up the idle, and it seemed to level itself out...once it warmed up. The 400ex is on cold blodded s.o.b!

[prolineracing]

hey idk if you this is any help but wen i had my 400ex off choke and floored it it backfired and the reason was cuz i had my airbox lid on but if you have your lid off then idk

[400exrider707]

Originally posted by jak1389
ok one more time, it is not the carb, the float is fine, i do not need to rejet, it was fine before and i had the same mods, i did adjust the needle considering the drastic weather change in climate.



yes i did run the plunger with the aftermarket cam i have, which is a hotcam stage 1. but i just found out i was 1 tooth off with the timing. i am guessing that was the problem. i will probably let everyone know later tonight.

So you have the stage 1 in without the mechanism on it I'm assuming, AND you still have the plunger and spring in?? Are you crazy! That thing is going to end up somewhere in your motor and cause some serious damage!!!

[daredevilearth]

change spark plug

[jak1389]

ok here it is, i am not running the spring and plunger in anymore, i had it in since august until about nov. no problems, the peice wont come out unless you take out the cam. any who, its out and the problem is not the sparkplug. the timing was off a scooch and made everything retarted. thanks for all the ideas everyone.

[ryder_trig]

I have sort of the same problem. My 04 400ex is completely stock. I stored it for a year after a Glamis trip. I completely drained the gas and the carb bowl before I stored. Now a year later it barely idles for about 10 seconds then dies. If I can get it to rev I'll hold it at about 4500 rpm (I have a trail tech with a tach) it will hold the rpm's for about 5-10 seconds then spuder, backfire and fall flat on it's face. I completely disassembled the carb and sprayed every port and jet with gumout carb cleaner, and it still stalls out. I checked the plug and it has good spark. The plug is black and suity too (not sure what that means. Any suggestions?

[Got4wd?]

Originally posted by jak1389
yesterday it was around 50. i started it up on full choke, and it started right up and idled nicely and i gave it a lil gas and it seemed to be fine. so i let it warm up for a few, then put it on mid choke for a little bit. after i took off the choke it acted as if it wanted to die out, and everytime i gave it gas it backfired. i am as of now assuming it is a carb problem.

Check your spark plug, they can tell all, right? How rich or lean you are. How the gas? I got a bad batch from Wawa, let it sit for a month, F*d my 400 for a second.

[SNO_DAY]

JASON, IF YOU FIND A SOLUTION PLEASE E-MAIL ME. I HAVE THE VERY SAME PROBLEMS WITH MY 99 400EX. I HAVE REMOVED AND CLEANED THE CARB 4 TIMES NOW, THE PILOT SCREW WAS SET AT DIFFERENT COMBO'S WITH NO LUCK. MY BUDDY THINKS IT MAY BE THE CDI BOX THROWING THE TIMING OFF, BUT I HAVEN'T HAD A CHANCE TO TRY A NEW ONE YET. GOOD LUCK AND IF YOU CAN HELP ME E-MAIL,

DARRELDAY@MSN.COM

THANKS.

[Honda#4]

Whats your jetting at?

[v0lcom13sn0w]

do you have the stock cam? if so is the decompressor spring in it still? because a lot of times they fall out when you take the motor apart and you dont even know it does

[v0lcom13sn0w]

check your carb and make sure all the vacuum lines are connected also. i just had a problem with my 400ex with my 450r carb i did the valves on it and i didnt remember to hook up the vacuum lines from my carb or atleast somehow they came disconnected and it wouldnt idle and it would pop on decel and accel, i looked at the carb and connected a hose and i felt like an idiot but it works now

[sc400ex_rider]

mine wouldnt idle the other day my intake boot had a crack in it from the 450r carb. make sure you grind enough away so the carb fits the boot.