400ex is pissing me off....help

[sica]

i have a 2003 400ex with a dmc alien full exhaust,a k&n air filter,dynojet jet kit with the clip on the third position on the dynojet needle the 155 main jet and the fuel screw 3.5 turns out.....it takes me forever to get it cranked and when i finally do i can ride it for 10-15 min and if i run it wide open it backfires and then just quits and will not start back for upwards of an hour....i have tried taking the air box lid off....i have tried leaving it on i have tried the 165,170, jets i have turned the fuel screw in and out 1/2 turns either way.....and after it will not crank after the backfire the only way to get it to run for several hours is to leave the choke on...if i turn it off it imediately dies........I NEED HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[a1965gt]

Im no expert but I will give it a shot...
I believe the metering limit of the air/fuel screw is about 2 1/2 turns meaning that after 2 1/2 turns it doesnt get any richer. im guessing you need to go to a bigger pilot jet (probably a 42 if you still have the stocker in there) I believe the air fuel screw only affects idle to 1/8 throttle, the pilot jet goes up to 1/4 throttle
If it runs better with the choke on sounds like you need to lower the clip on the needel down to the 4th position from the top. The needle and seat control fuel from 1/4 to 3/4 throttle. The main jet controls fuel from 3/4 to full throttle I cant imagine you needing anything more than a 165 with your setup.

There may be somthing else wrong with your quad my friend has the same exact setup but he ran the stock jetting and it ran fine (but a little hot) we just recently put a larger main jet (165 I think)in it which made it run a little cooler and faster but like I said it was running good with the stock jetting.
Hope this helps.

[sica]

well see the instructions with the dynojet kit says to turn the screw out 3.5 turns....so i just dont know what to do...i have tried to put the clip on the 4th position and the bike ran horrible.....and it was way too rich....i dont know what i am going to do.....what would make it not want to start?????? and why is after ridding it hard for a few minuits make it backfire and then not crank again???

[sica]

what is the stock position of the fuel screw...how many turns out ????

[kargaaro]

2.5 turns out....and go to a bigger pilot (42)

Your main could be rich too. Keep troubleshooting.
Main 158
pilot 45
needle 3rd notch
2.5 turns out

[dariusld]

Why does everyone have such a hard-on about changing the pilot jet? Both my bikes have stock pilots and have never had a problem with my jetting, or my bike running badly, or starting. Your jetting doesn't sound far off enough for your bike to be doing all that. I did what my dynojet jet kit said and it ran fine.

[promisc]

Its seems that after fews mins, you run WAY to lean so the engin runs hotter, backfire and fade. It takes time to cool down and the gas to fill the carb bowl. Look at the fuel line and try to run it on the reserve (even if your tank is full).

[a1965gt]

Why does everyone have such a hard-on about changing the pilot jet? Both my bikes have stock pilots and have never had a problem with my jetting, or my bike running badly, or starting. Your jetting doesn't sound far off enough for your bike to be doing all that. I did what my dynojet jet kit said and it ran fine.
dariusld,
Its not that you NEED to change the pilot, like I said my friend has the same mods (DMC and K&N) and his quad ran fine with completly stock jetting. That is why I also think there may be somthing more going on here than just a jetting issue.
However if you want to tune your quad properly the pilot jet is definatly worth looking at, you would problaby notice a small improvement if you were to change your pilot jet. Not in top speed but in off idle throttle response and ease of starting.... at least that has been my expierence with the pilot jet.
Besides the jet only costs like $5 and is easy to install, should only take about 20 minutes....
Running good doesnt necessarly mean running at peak performance.

[dariusld]

Originally posted by a1965gt
dariusld,
Its not that you NEED to change the pilot, like I said my friend has the same mods (DMC and K&N) and his quad ran fine with completly stock jetting. That is why I also think there may be somthing more going on here than just a jetting issue.
However if you want to tune your quad properly the pilot jet is definatly worth looking at, you would problaby notice a small improvement if you were to change your pilot jet. Not in top speed but in off idle throttle response and ease of starting.... at least that has been my expierence with the pilot jet.
Besides the jet only costs like $5 and is easy to install, should only take about 20 minutes....
Running good doesnt necessarly mean running at peak performance.
I'll race your 42 pilot to my stock pilot anyday of the week:D

[kargaaro]

Originally posted by dariusld
Why does everyone have such a hard-on about changing the pilot jet? Both my bikes have stock pilots and have never had a problem with my jetting, or my bike running badly, or starting. Your jetting doesn't sound far off enough for your bike to be doing all that. I did what my dynojet jet kit said and it ran fine.

I've had quads run fine on jetting that was way off. You will get maximum performance and protect your motor by jetting each jet one at a time until it's right. I'm sure your quads run fine but it's something you have to do when you do mods. Don't be lazy or ignorant.

[SLB400EX]

Originally posted by dariusld
Why does everyone have such a hard-on about changing the pilot jet? Both my bikes have stock pilots and have never had a problem with my jetting, or my bike running badly, or starting. Your jetting doesn't sound far off enough for your bike to be doing all that. I did what my dynojet jet kit said and it ran fine.

Everyone's quad is different.
Mine was a pain in the butt to start in colder temps, so we bumped up my pilot jet to a #40...starts lots easier now.
My husband's quad on the other hand, likes the stock pilot jet. His will start w/ no problems in colder temps.

[cals400ex]

my bike didn't even to seem to start much easier after installing a larger pilot. however i think it is good to put a larger one in even though a pilot won't help on performance. my bike ran really lean at idle with my sparks pipe. my headers would glow. so, i installed a 45 pilot and turned the fuel skrew out 2.75 turns and it isn't lean anymore.