400ex carb on 300ex jetting

[Puff_Pryor]

hey guys i bought a 400ex carb for my 300ex and i was runing stage 2 jets and i want to know what size jet to put in and i think im gona put in a hi comp pistion and cam will i have to change the jets then oh yeah my bike has a power core 4 pipe k&n hi rev box and vented air box plz help me at least find a place to start oh yeah im below 3000 feet

[bwamos]

http://www.exriders.com/vbb/search.php?s=&action=showresults&searchid=1098530&sortby=lastpost&sortorder=descending

[RiderTRX400ex]

i just did this to my buddies 300 recently, i ended up with a 155 main

[bwamos]

Sounds about right.

Oh, yea. Everytime you change anything in the air pathway on the ATV, you will have to rejet. Compression, cam, pipe, filter, venting, porting, lid on/off, quite core in/out, etc.. Of course with he quiet core you can just jet it for the core out, and let it run a little rich with it in.

[Honda TRX250ex]

how much extra power does it add to the quad?
could you do it to a 250x too?

[Puff_Pryor]

right know i have stage two jets by dynojet andi think the jet i put in was a 138 and it is runing with air box lid off is that right it is with the stock carb

[Puff_Pryor]

bump

[bwamos]

Originally posted by Puff_Pryor
right know i have stage two jets by dynojet andi think the jet i put in was a 138 and it is runing with air box lid off is that right it is with the stock carb

Stock 300ex carb?

What are your mods?

138 sounds rich. (of course dynojet has a different numbering system, I think they actually use Mikuni jets w/ an adapter).

FULL pipe (header and silencer) + K&N + no lid = 128 main +/-, Needle up 1 from stock, and the stock pilot should be fine. 2-1/2 turns out from seat on air screw (if I remember right, I'd check into this one though, it's been a long time, lol).

This is what I ran at 1000ft on my 300, if that helps.

If you have the dynojet kit for the 300ex, just follow the instructions. Mine came out dang near perfect back when I first got my 300.