Jet Suggestions

[trex trx400]

Hey all, here is my situation...I have a 400ex just ordered big boy full and k&n gonna mod the air box lid. Am i going to have to redo the jets? if so can i get some sugggestions for where to start. I've already read alot on jetsrus.com but no where does it says where to start.

oh yea in a few months i'll be going either 416/426 with hot cam and maybe a 450 carb. so think i'll be alright for few months without the re jetting? and i'm not a racer just a weekend trail rider. thanks

[rocky_mtn_honda]

you could either start by using the search button on the forum....or since you chose the other route, maybe take the carb apart and pull the jets and let everyone know what pilot and main is in it...you could also start with installing a new plug after you do the mods, and go ride it for good 30 minutes then pull the plug and check it...maybe post a couple before and after pictures of your plug color...just so you know, you get a lot more answers here when you do your homework before you present your questions
and as for taking care of the jetting now or later, an improperly tuned carb can quicky cause extra fatigue on your engine
i'd handle it now if i were in your shoes
welcome to the forum ;)

[trex trx400]

ok well i've read the sticky jet help....all of it please...please please show me where it answers my question. I just want to get a starting part i mean **** i can do that in my house before i even step into my garage to me that just seems logical i don't know guess months of reading forums will change my perspective???


all i want is somebody that actually knows about big gun exhaust to say yea i started 150 and 152 worked better see how that runs on ur engine...understand? i mean maybe i'm wrong but i was taught to work smarter not harder but i guess it's easier for me to install new jets "just a random number since i have no CLUE where to start" stop check the plug and then i should know where i'm at or somebody that's not a douche that has been in my shoes could not be a sarcastic prick and share some knowledge. please if i'm wrong let me know please. i thought forums were for this.

i've been on here for week str8 i've been through so many jet threads jet i've not found an answer hense the question. thanks

Josh

[trex trx400]

oh yea its a stock 07

[rocky_mtn_honda]

have you pulled the jets? or are you just assuming we know whats in there because its stock? pull the jets and look at the plug...that tells you your starting point. say you have a 148 standard main, if your adding more airflow with your exhaust, then you want to adjust your fuelflow to match, which in turn provides you with a nice cardboard color on your new spark plug after riding it for a good 15-30 minutes...no one can tell you where to start because there are too many variables that factor in when jetting a machine, avg. temp, altitude, even barometric pressure plays a role...its truly something you do have to experiement with. whats your altitude? avg. temp? color of plug? what jets are in it now?

[trex trx400]

the machine is stock so from what i read it's 148 n 38. i'm in nc now 300 el about 60 deg now no i haven't even installed the exhaust yet but i'm having to order everything off line i live bout 2 hrs away from a decent atv shop in jacksonville so i don't want to get my exhaust install it and then have to wait another 2-3 weeks to ride my bike that would blow. i'd rather get a round-a-bout number from you and just go ahead and order plus/minus 3 jets
money isn't an option time is. please help. and thanks in advance

[rocky_mtn_honda]

in that case, if it we're me, and i went riding at multiple elevations (which i do) i have the 140 main and the 38 pilot, but i did order a 142 and 148 main for diff. altitudes...jets are cheap, easy enough to drain the bowl and use a 6mm socket and just change it before i hit the trail...you shouldnt have to mess with the pilot
you should be able to adjust the rest if you had the 140 and 142 main
EDIT : maybe order the stuff and put the exhaust on but dont mess with the jetting yet...run it with a new plug and ride it through all the gears seeing how it pulls and reacts...then pull the plug and check it...that will definately give you your best reference as to where to go next

[trex trx400]

ordering a 140 and 142 we'll go from there hopefully with ease.

thank you and much appreciated rocky.

[rocky_mtn_honda]

actually im quite sure i had that backwards...sorry hope you didnt order them yet...lol im pretty sure you wanna go up in jet size since you've already introduced more air, you need more fuel, my bad!

[trex trx400]

no didn't order yet...so get a 150 n a 152 should be good for me?

[rocky_mtn_honda]

i'd say its a good start...just remember the idle/throttle response and the plug will tell the tale of how the carbs tuned
and make sure and test with a new plug...
white=up in mainjet
black/wet=lower mainjet
brown/cardboard=moneyshot!