O.K. I have a 2007 klx250S all the mods running a two brothers pipe, 128 main jett, 40 pilot jett out 2 to 2 1/2 turns,
no air cleaner lid, I live at sea level. The plug looks black and their is a little black on my fender from the pipe.
Well it seems a little loud so I bought the P4 insert for the pipe, much better.
So im thinking about going back to a 35 pilot with the fuel screw out 2 1/2. That should help with the gas slurping.
I hope it will help with the black plug and fender. Also I was thinking of dropping the main down to a 125.

What do you think?

 

for just a slip-on, those jets and airbox modssound a little too rich for just the slip-on. I had a full system BigGun and those were my settings minus the airbox lid removal- I just enlarged my snorkel hole. What about your needle setting? Your oem header doesn't flow as good as an aftermarket so........

edit: hey, I did a little research myself since I'm far from a pro too. I found this writeup very informative and easy to understand. good luck.

http://www.highlifter.com/forum/Basi...1872049/tm.htm

 

Check outthe jet specs in my signature, bike runsstrong andI have the 2 bros with the P4 tip. Im at about 500-800feet.

Drilled the slide hole with a #32 drill too, but that won't effect the "richness"

 

Ditch the #40 pilot and run the #35 with the screw at 3 turns out and the needle at the 3rd clip with a 128 DJ main.I'm also at about 450-600 feet and with an FSW header and FMF P core 4 it seems to work the best.
If you have a stock header you may want to try a 126 main with needle the same (3rd).The 40 pilot is way to fat as you will notice almost no need to use a choke to start the bike even into the 40* range.
Just my suggestion as i have changed my jetting about 20 times to nail mine down at my elevation.Yours may be close.

 

you must remember that i'm also using a DYNOJET size for reference....also no airbox lid.The DJ 128 is close to a 125 Keihin main.....not sure what you have as you never specified.I also have a quiet core in my FMF but never saw a power or jetting difference with the swap......The FMF quiet core seems to be a different insert than some of the other pipes out there from what i have seen.It is just a 6" solid (non- perforated) tubular insert that slides in compared to a baffled perforated insert core .....not sure what the 2 bros is.

 

You have it backwards--DJ are bigger.

Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

 

I'm not wrong i just typoed....I meant a 135 and not a 125.....sorry for the confusion.

Man that was an easy cover up......

 

Thanks for the replies, I have the N1 needle or what ever its called, on the 2nd spot
Not sure what that does tho. My jetts are factory jetts forthat carb keihin.
So back to the 35 pilot and I think I will try the 125 main I bought also.

 

hey guys great posting..im learing a lot..
i have a 2200k klx 250. im gonna put a 300 big bore on it and leave the carby stock.
however following work750 advice im gonna try a #142 and a #40 pilot.
what are your thoughts on this?
really wanna know.
btw im at sea level and am adding a staintune header and pipe.
"A real easy upgrade is to fit the KLX300 barrell/piston/gudgeon/clips. It will significantly up the power from a measly 18HP rear wheel to about 25-27Hp dependant on other mods. But most of all is that it will really increase the torque. Now this is the tricky bit. With all the other mods I recommended in an earlier post (airbox lid etc) I would actually drop in a #142 main and a #42 pilot. Bear in mind I am at sea level in a dry warm climate. Yes I know it is a smaller jet than the 250cc. Don't know why. Some think it may be to do with intake air velociity over the main jet. Don't know. Don't care. You may even find you need to go down to a #138 main. The pilot stays the same though."