400ex carb on 250x

[stonerider250x]

i baught a 400ex carb and it had the choke removed and a 155 main and a 40 pilot jet's. my old carb had a 122 main and a 32 pilot. i put the 400ex carb on and it ran like crap (obviously way to high) then i took the jets pout of the 250x carb and put them in the 400ex carb and now its poppin like crazy and bogs out when i gas it hard:( . i dont no what to put in it and was wondering if any of u guys had any ideas?

[stonerider250x]

i rode it again and now when i am going in any gear and let off and pull in the clutch it stays at the same rpm as it did when i was still holding the gas then idles down really slow:confused:

[TheX1992]

sounds to me the 155 was way to rich, then the 122 was way to lean...at least you got a high and a low to work off of....try a 140 or something in the middle and see what happens.

[Red Rooster]

I am running a 165 main and a 42 pilot, I forget if the needle clip is in the middle or 1 down (one adjustment richer). I have the choke removed, uni air filter vents, uni filter, fmf megamaxII with 9 discs and no quiet core. It is jetted and running perfectly. But this is on a 300ex, not the 250x. How exactly was it running like crap? Was it better with the 155mj than with the 122? What is your air fuel screw at? Mine is at the stock 400ex position..... Whatever that is. I want to say 2.5 turns out. definitely the 122 is wayyyy to lean. you are shure you have a good airtight seal from the filter to the carb and especially from the carb to the head? Hope this helps.... reckless@drenthe.net E-mail for more help!

[stonerider250x]

it was runnning a little better with the 122. My airskrew is about 2.5 and when i said running like crap it wouldnt stay at an idle it would stay reved high for about 10 seconds after i let off the gas but it wasnt really popping that much. I dont no what this means :confused: i think im gonna get a 130-140 (not sure yet) main jet and see how it runs.

[stonerider250x]

i got a 130 main jet the other day and now the only problems are when i first crank it up it puffs out 1 cloud of black smoke, and when its ideling if i rev it up kinda high when it idels back down it pops but it doesnt do that whn im riden it:confused: also when im riding it it still idles back down really slow. i think if i get a bigger pilot jet it should quit that but i dont no:confused: right now its got the 40 in it which does better than the 38.

[Out_Sider]

Im running a 135 main jet, and a 38 pilot, with my mods, but i have a stock carb. If i get a 400ex carb, i'll probably run with a 138 main and 40 pilot.... but i dont really see how the pilot jet would make it blow smoke- all it does it make it idle, it doesnt have much to do with anything else. I would have went with atleast 135 jet in the 400ex carb, instead of the 130.

[stonerider250x]

i no that the pilot jet wont have nuttin to do with the smoke:huh :huh im gonna get a bigger pilot to make it stop ideling down so slow. i only blows out smoke when i first cranke it up anyway. i think thats cause its still a little lean so im prolly gonna get a 32. And by the way i cant really base mine on what u have because the 250x has a smaller stock jet than the 300ex:rolleyes: