jetting HELP asap

[wanta450]

i have 05 400ex just rebuilt with hmf full system stock airbox with uni filter and hotcams stage 2 cam bored over just enough to rebuild put in 10-1 comp piston and had head ported and polished . right now i have a 180 main jet in it and it runs fine up to about third to half throttle after that it dies out if i turn choke on it will not cut out .. what size jet do you guys recommend from experience

[leasureryan]

I have the almost exact same setup...only I am running a 450 carb, but that doesn't change the jetting much. I am at a 185 main, and still rich. You motor should run on that 180 jet...and IMO, that is a little fat still. It should run...I say you have a problem elsewhere.....like an air leak, or some other mechanical/electrical malfunction. who did the head work? And did they have a flow bench? It may still be carb issues...but man...that thing should run....did you double check EVERYTHING?

[wanta450]

yeah it was flow benched when done i am planning on running the 450 carb but was trying to get the stock carb right first as far as i know everything is on and tight i guess i could check more this is gonna be stressful i bet

[rideracelivemx7]

ewwwww way to much fuel lol my 170 was a just right, do a 170 and 42 pilot, should be goldem, im running a 185 on my crf450 lol and that needs alo tmore fuel than the little 400 does

[rideracelivemx7]

waiitttt you put a 180 on stock bore!? you crazy man

[BERT306]

Originally posted by wanta450
i have 05 400ex just rebuilt with hmf full system stock airbox with uni filter and hotcams stage 2 cam bored over just enough to rebuild put in 10-1 comp piston and had head ported and polished . right now i have a 180 main jet in it and it runs fine up to about third to half throttle after that it dies out if i turn choke on it will not cut out .. what size jet do you guys recommend from experience


so from half throttle to full it sputters?? but does fine w the choke on....

Sounds to me its too lean, and thats why turning the choke on cures it.

CHOKE=RICHER MIXTURE

[wanta450]

thats what i thought but main jet seems way big when it was slip on cam and uni filter stock box i ran a 160 main and it was great but when mods were done it cut out went to 168 and it cut out went to 180 and still cuts out

[BERT306]

i agree that 180 is too big for your mods, maybe u have another issue.

Try letting it idle and spray some carb cleaner around the intake boot and carb. If the sound of the motor changes, u have a leak somewhere. Easy to do and worth a shot.

[wanta450]

bump

[Duke Nukem]

I ran a 175 main on my old 440 and ran like a champ.

[wanta450]

well i checked for leaks on boots with carb spray and no luck so i say i dont have a leak. still when you put choke on it will rev to the moon fine but ive tried clear up to a 200 and cant get it to run right it just blubbers and cuts out i guess now that i bumped my pilot from a 38 to a 42 ill start back down at a 170 jet and see . i might just have way to much fuel even tho it acts same as when i had the 160 in it which is what we ran before the port and polish was done. grr this is so frustrating

[wanta450]

bump