help my 300ex carb jetting problem

[clay3007]

i cant seem to get the carb jetted correctly... ill give the specs first..

ported and polished head,
kibble white springs
hot cam stg 1
fmf header
hmf slip on
76mm weisco 11:1 hi comp piston
400ex carb
uni filter
no air box lid
14/38 gearing


okay so i got it all built and then i started with a 135 main jet and i have a 42 pilot jet because the choke is removed.

with the 135 and 2nd clip from top at bogged bad pulled plug and its black *** hell. so i bump down to a 125 and bump the needle all the way to rich and it comes out brown but it seems like its bogging at like 3/4 throttle.

anyone else have these mods done to there 300?

[fmftrx300ex]

try a 128 at half needle if it runs good till 3/4 tht means you main jets to lean and ur needle effects up to around 3/4 after tht its mainly the main jet

[clay3007]

Okay ill try that. I had the 135 in there and there was a pool of gas in the black boot between the carb and head.

[JOHNDOE83]

In the 400ex section also in the atv how to's section, I have a thread on how to jet and how to read plugs.

So far its helped alot of people, I get compliments all the time, give it a shot and good luck.

The thread is called, plug reading for jetting...info.

[clay3007]

okay well i bumped it down to a 40 pilot and got the needle correct but it seems lean in the top end and i have tried every jet up to a 148. i dont think i would need that big of a jet. but then i also read that when u pipe a 400 i need to change the main jet to like a 160 or something.

[JOHNDOE83]

my 440ex doesnt even need the needle on the fourth clip.

just looking at a plug will NOT determine your jetting, thers alot that goes into plug reading other then just looking at it, the porcelain color has NOTHING to do with determining jetting.

look up my jetting thread, better yet ill post the link right now.

[JOHNDOE83]

here is the thread if you havent already read it.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=plug

[clay3007]

No i changed the needle back to the 3rd clip down from the top and put a 40 pilot jet instead of 42. I just need to get the top end correct.

[m0t0xk1d]

i ran a 172 in my 300 all last year with a 400ex carb and it was perfect. remember now that you have a bigger carb letting more air through you need to let more gas through. so a 172 may seem big from the stock but the carb is also bigger then stock

[clay3007]

Okay. Im almost dialed in on it. I have a 168 in there now and its still just a bit lean so i got a 170 and a 172. Hopefully that solves it. How did ur bike do on gas?

[m0t0xk1d]

are you talking gas mileage wise? well i could fill my tank up and practice at the track all day without having to fill up again and that was like 10 - 6 and my friend wioth a baster had to fill up four times

[clay3007]

I was just wonderin how long u can go on a tank of gas since it has that big of a jet in it.