Jetting help 2011 six days 300ec

[Colemanian]

I just bought this bike today. Road it for 10 min then tore it apart. ( I have a race coming up, short on time). I'm sending the head to rb designs. I have a 38mm carb it says AL1 O BEN on the side. It has

175 main
40 pilot
#7 slide
N1EF Top groove
3/4 turn air screw

I have a jd red laying around that fits a 36mm carb. Where should I start?

[Jakobi]

42 JD Red#4 180 is JD's recommended for sea level. You might find it'll run a bit better in clip 3 though.

If you want to work outside these specs either
42 N3CJ#3 178, or
42 NECJ#3 175, will be close.

If the J feels a bit flat around 1/4 idle consider moving a step richer on the diameter.

The jetting specs you posted are stock and are crap. You'll notice the idle screw is probably turned in quite a lot (raised slide) to compensate for the overly rich idle mixture, and that the air screw won't have much effect on idle. Be sure to check the float level as well. Its essential. See the sticky at the top of this section.

[Colemanian]

I'm a little confused about the mm of the float. From what I've gathered, you need to raise the float so the fuel shuts off earlier right?

[Jakobi]

The float height is the distance from the join between carb and bowl, to the lowest point of the floats. The fuel level is the distance from the bottom of the bowl to the point where the floats close the fuel. You want to reduce the amount of fuel in the bowl a bit to reduce splash over (due to angle of the carb). Thus you want to increase the float height by a mm or two, or reduce the level of the fuel. You want the floats to close fuel supply earlier.

For best results I suggest setting the carb up to a fuel supply with the bowl off and bench testing so you can visually see when it cuts the fuel off.

[Colemanian]

I had planned to send the carb to be modded but I'm going to give your specs a chance first. What do you think the manners will be between the jd needle to one of the others you suggested?

[Jakobi]

Both the JD Red and NEDx needles will be quite linear in their power delivery. They are both triple taper needles.

JDs taper profile is lean, rich, lean.
Suzuki (NEDx) is lean, rich, richer.

I like the Yamaha/KTM needles (N3Ex). They provide more of an MX style hit. They're a dual taper needle that runs rich to lean. The result is a smooth and torquey bottom end, and an arm tearing top end, with a reasonable transition between the two. I ride the clutch heavily to smooth the hit and bring the bike onto song in the flick of a finger. The rest of the time its happy chugging around off the pipe.

I only tried the JD Red briefly and felt it was too rich in clip 3 for me. The suzuki needles are very good all round as well. If you have the red needle give it a try first! The others will only set you back $10 a piece if you decide you want to try something else.

[Colemanian]

I've installed the jd red in the configuration you suggested. Now I've just got to wait on the head to see how it runs. Thanks a lot.

[Jakobi]

No worries. Hope its close for you.

[Colemanian]

I called jd today to verify my needle out of my KTM kit would work on my gasser. They said it would which was a plus but they said their recommendations were 180 40 4th position. I know you said to use the third position, but I thought you might like to know they said to use the 40 pilot not the 42. Thanks.

[Jakobi]

No worries chief. I was just shooting from memory. I do have the actual documentation here for the JD needles as well. One size difference in pilot isn't going to make a huge difference that can't be worked around with the air screw. I also suggested that it may work better in clip 3. Nothings set in stone when it comes to jetting and trial and error is the aim of the game.