Jetting: 2011 250 (38mm carb ASII)
 

Hello everyone.

I'm going to be buttoning up the 250 top end some time soon and as such will want to get a baseline to set the jetting at.

Currently as a 300 I am running 42 N3CJ#2 172 at 300M-1000M 25-35C RH 50-100%. First impressions are to go up a size or two on the pilot and main and 1 clip richer on the needle.

Very interested to know what others are running in their 2011 EC250's and also if anyone has any info re the fuelling requirements between the 250 and 300's that would be great also.

PJ 40
MJ 178
NEDW #1
AS 1.5

Runs great from mid 60's to mid 80's, but it is probably a little rich on the MJ. I've been happy enough with it that I haven't experimented any more with it. I tried a 38 PJ, but it didn't have the same pop of off idle.

N3EW gives it a stronger mid, but it comes with the price of a more abrupt hit.

What altitude? Sounding very similar to what I would run in the 300 at the moment. I know all about the N3xx hit! I LOVE IT!! :D

Approximately 600ft-700ft

Approx 1000' elevation, temp from 50 to 70 F
Ipone samurai racing synthetic oil at 50:1
AS II 36 mm

40 P
AS 2.5
JD Red clip 3
175 M

Rock solid idle, no ding ding just a steady whir
Almost no spooge
Very linear power, perfect for off trail exploring
Plug check shows mostly gray with some light brown

Note: I can do all my riding rarely ever needing more than 1/4 throttle (I marked the grip and have glanced at it to check position while riding)
I haven't accurately checked mileage, but it's good; at least 10 km/litre

If I were racing on more open terrain , or just trail riding your setup is almost exactly what I would be using with that needle, 45 pilot, start@#3 on the needle, and a 175 main.

What I'm currently using for the weather conditions and terrain that I will be racing in dictate that I need a flatter power curve than you, so I'm using an:

NEDJ #3
40-pilot
172 main

Those are the exact same settings i'm running on my 12 300.

500'-2500', 50-70 degrees F

172 main
40 pilot
NEDW needle, 3rd clip.

I ride tight, snotty woods, this combo works great.

At this point it almost looks like theres nothing in it regarding fuelling requirements between the 250 and 300. The smaller displacement must require less fuel, but must meter less due to the smaller signal. I was expecting the weaker signal to mean a few sizes up in jets. I'll still start off on the rich side and dial it back in just to be safe, but won't be shocked if I end up where I am already.

Keep em coming!

Remember its a 250, so by nature its going to hit a little more than a 300. Don't go too far trying to jet this out or you will be too lean. In my experience they go a little flat and like to be on the rich side if anything. Mine is one of the fastest 250s I have ever ridden, and it has a spoogey silencer and a black plug.