400ex Emergancy carb problems!!

[MX MadMann]

ok guys its like this , all i have is a sparks pipe , k and n filter , and jets in my carb as far as the motor goes. my carb has a 155 main , 45 pilot , and my needle is on the second clip from the top(stock needle). i run 93 octane fuel. i left my 400 sittin for a month or two because of remodling and getting moved into my new house. i went and cranked it up yesterday , i was pumpin the gas from 3/4 to wide open when it fired off and i was sittin there reving it from 6000 and up up and down up and down. i let off the throttle and it idled down to idle speed and ran fine. i then proceded to hit the throttle and it instantly died. yet it fired up again and would run on the top end , and it would idle well. i can ever so slowly ease the throttle on from idle and it will slowly build RPMs to a certian point , but if i hit the gas even barley , it dies. the last time i ran it , it was sputtering really bad thru the midrange yet when i punched the gas , it ran like a scalded ape.i really need help with this so i can get it going for this weekend. any help would be greatly appreciated.

thanx , casey

[VegasEx'r]

Nice looking quad, how do you like your exhaust? Sounds like you're getting too much fuel from your pilot jet. Try dropping down to a 40 & see how it does. Or you could try a 38 & put the needle back on the 3rd position, either of those should do the trick (of course I am not as smart as I think I am, so it might not do the trick :D ).

[NVR2L8]

If you raise the clip position from the 3rd to the 2nd from the top, you're leaning out the mixture from 1/4 to 3/4 throttle. Move the clip back to the 3rd slot from the top and see how it runs from 1/4 - 3/4 throttle. If it seems a little lean thru this range, move the clip to the 4th from the top to richen it up. Just remember that raising the clip "lowers" the needle and leans out the mixture by allowing less fuel to pass by it...conversely, lowering the clip "raises" the needle in the needle jet and allows more fuel to pass.

For your mods you might be a little too big on the pilot jet...I ran a 42 with similar mods at one time and it seemed just right. Also remember to adjust the fuel screw after changing the pilot to get the best off idle response when lightly bumping the throttle from idle (a little hesitation is normal). As far as the main jet is concerned you're probably in the ballpark, but you should really check the plug after doing a WOT run (do a "plug chop" by killing the ignition while also pulling in the clutch and rolling to a stop). You want a nice light brown color.

[Leo]

drop the needle clip down to the second notch from the bottom...

if that doesn't help bump the main jet up a size or two...

you might also want to try a 40 or 42 pilot, but I'd think I'd worry about the needle / main first...

Leo

Check to see if your accelerator pump is working. It might be gummed up from setting so long.

[Red Rooster]

Your needle is too lean, put the clip on the second from the bottom (pointed end) like NVR2L8 and Leo said

[MX MadMann]

i like that pipe pretty well, it ran really well for a little while but then it started sputtering in the midrange. it sounds like a harley davidson on acid when u hit the gas. its insanly loud. ill try to mess with the carb today. i think im gonna richen it up a little bit with the needle and if that doesnt work ill go get me some more pilot jets. i was also wondering about that fuel mixture screw on the carb itself. sparks racing told me to use a 45 pilot , 155 main , and the needle in the middle.

[gojk]

Did you put new gas in it. It could just be old gas.

[nakomis0]

I'd get some fresh gas in there too.

[MX MadMann]

well i fixed the problem , i was messin with it late at night and i diddnt have time to tear it down. turns out that my needle had come up and completly out of the hole in the carb , it then moved over to the side and got stuck , so it would idle fine and tun on top end. guess ill look before i ask questions next time haha.
thanx for all the suggestions guys.

now i have another problem , its runnin too rich thru the midrange and i already put the needle on the second clip from the top. i was wondering if i needed to change the pilot jets out from my 45 which was what sparks racing suggested. im afraid to lean the needle any more becase it runs fine from a little over 1/2 throttle and on. it seems to be from just over idle to 1/2 throttle that it sputters and black smoke comes out( it doesnt backfire and it smells like gas so i know its rich). if u have any knowledge on the fuel mixture screw it would be helpfull becuase i think that might be another problem. sparks told me to turn it 2 turns out and thats where its at. any more suggestions would be greatly appreciated


thanx, casey

[NVR2L8]

I still think you should be running the needle on the stock position, which is on the 3rd groove. Since you increased airflow into the engine with the K&N, as well as flow out of the engine with the Sparks silencer, you should have to go up a few sizes on the pilot and the main to richen things up. Having to lean out the needle goes against the grain of richening up the mixture after intake/exhaust mods. FYI, the stock needle position should be okay for your mods, since my experience...for whatever that's worth :D ...has shown that the needle position is more forgiving when doing minor aftermarket mods.

Go back to the 3rd position on the needle, and try a slightly smaller pilot jet...I'd try a 42. Adjust the fuel screw to an initial setting of 2 1/2 turns out. Then after making the changes warm up the engine to normal operating temp, and then adjust the fuel screw out (rich) until you notice a change in idle speed, and then in (lean) until you again notice a change in idle speed. Then after noting this upper and lower range, find a spot close to the middle of each two where you get the best off idle response when slightly wicking the throttle. A little hesitation is normal...

Here is a good pic that shows the ranges of each circuit: