I've seen a lot of different things recommended for this somewhat tricky bike when it comes to jetting. I've a few different needles, pilots, mains, an s-8 nozzle and need to know where to start, considering my conditions. Right now the carb is stock except for the pilot, which I went from 30 to 32.5 and main from 420 to 410. Many of the posts recommend stuff for bikes in higher altitudes. I am at sea level, in new england, with 50-60 degree weather and have added a works pipe, shorty silencer and a v-force 2 reed valve. I also will usually run VP-C12. I changed to 50 teeth in back, but still the bottom isn't great. Any recommendations?
2003 CR250 Jetting
- Thread starter fittro
- Start date
motor work
I dont think the bottom on an 03cr can be great. It can be acceptable with some motorwork, even above average maybe, but the bike suffers from lack of bottom. Ive been through the kehin conversion, no joy, (some swear by it, I swear at it) jd jetting kit, s-8 nozzle,(the kit is very detailed on setup hope you have a full day devote to jetting and testing) it helped the lower mid to top for me but did little on the bottom, there is a link to adjusting you powervavle to 12mm on the aft cable that seems to help out alot of guys, mine was very close to that so I didnt see much there either. My Rm on the other hand has pretty nice bottom as is, but not as nice or smooth mid to top as the cr. Wish I could smash these two motors together. :nod: I just always kept a finger on the trigger with the cr and worked overtime for clutch kits.
I dont think the bottom on an 03cr can be great. It can be acceptable with some motorwork, even above average maybe, but the bike suffers from lack of bottom. Ive been through the kehin conversion, no joy, (some swear by it, I swear at it) jd jetting kit, s-8 nozzle,(the kit is very detailed on setup hope you have a full day devote to jetting and testing) it helped the lower mid to top for me but did little on the bottom, there is a link to adjusting you powervavle to 12mm on the aft cable that seems to help out alot of guys, mine was very close to that so I didnt see much there either. My Rm on the other hand has pretty nice bottom as is, but not as nice or smooth mid to top as the cr. Wish I could smash these two motors together. :nod: I just always kept a finger on the trigger with the cr and worked overtime for clutch kits.
You will notice the most difference on the 03' CR250 leaning your needle..If you're running straight VP C12 you can go much leaner all around than the stock setup...410 main is too rich with C12...Basically you need to experiment and go leaner across the board until it's crisp and responsive yet not surging or knocking (like it wants to idle or rev higher with the throttle off). Start with leaning the main until it's right...I'd try a 400 next and so on until 3/4 to full throttle is spot on...Then the needle, then pilot/airscrew ect ect...And on different temp days you can go richer or leaner depending on conditions...
I have a high compression motor modded by Eric and am currently running C12...Here are my jetting specs. altitude is about 600ft . temps in the 70's
Main 370
needle stock clip raised 1 notch
stock pilot (getting warmer may go one step leaner) 80's the other day had a slight hesitation off the bottom.
Now, the modded motor needs a leaner set up and even more so with the race gas...But with the straight C12 on a stock motor you can go right to the edge without too much problem...
With these specs it's very crisp and the silencer is dry... I suspect yours will need to be a tad richer on the main being at sea level and the lower temps.
I have a high compression motor modded by Eric and am currently running C12...Here are my jetting specs. altitude is about 600ft . temps in the 70's
Main 370
needle stock clip raised 1 notch
stock pilot (getting warmer may go one step leaner) 80's the other day had a slight hesitation off the bottom.
Now, the modded motor needs a leaner set up and even more so with the race gas...But with the straight C12 on a stock motor you can go right to the edge without too much problem...
With these specs it's very crisp and the silencer is dry... I suspect yours will need to be a tad richer on the main being at sea level and the lower temps.
Similar Topics
