Jetting a 2002 CR250
- Thread starter slickpuss
- Start date
I think bedell's right, definitely lean it up, especially the pilot. I know at our altitude (5500-6000) they are very sensitive to jetting, especially on the pilot and the needle. Not to beat a dead horse, but have you checked the adjustment on the powervalve cables recently? They can get sloppy quick and that might account for some of the change on the top end as well. Let us know what the results are.
bedell99
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- May 3, 2000
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Andrew
30 pilot, between 1 1/2 to 2 turns out
Bey30-76 needle in 2nd clip
340-350 main
I run Sunoco 100 octane race gas at 40:1, In the summer I used a 340 main and put the clip in 1st position. My jetting is about as perfect as ypu can get on this bike. I live in Denver and race between 5000-6000 ft. I use Mobil Mx2t oil. Never any spooge, very clean plug. My bike is stock. (Only 1 more week of racing and it is off to Eric Gorr for my Christmas present to myself)
30 pilot, between 1 1/2 to 2 turns out
Bey30-76 needle in 2nd clip
340-350 main
I run Sunoco 100 octane race gas at 40:1, In the summer I used a 340 main and put the clip in 1st position. My jetting is about as perfect as ypu can get on this bike. I live in Denver and race between 5000-6000 ft. I use Mobil Mx2t oil. Never any spooge, very clean plug. My bike is stock. (Only 1 more week of racing and it is off to Eric Gorr for my Christmas present to myself)
This should help. The leaner pilot & air screw adj should help it idle some, right? Hey bedell, I just pulled my motor out last night and will be sending it to Eric sometime this week :) I guess that will shoot these numbers to pieces when I get it back.. Oh well! Thanks again, I appreciate the feedback.
-Andrew
-Andrew
bedell99
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- May 3, 2000
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NO oxygenated gas calls out for a bit richer jetting. The reason I have been running race gas is the pump gas here contains 10% ethanol. As most people know here ethanol sucks for a two stroke engine. As for the temps we have been hovering around 40-45. I'm curious to see how the jetting will be affected when I get my engine done by Mr. Gorr. I have 2 races next weekend and I go into hibernation for the month of January. I'm also of thinking of getting a rad valve, but to be honest this bike has treated me well. The only thing I disliked about it was the jetting.
Erik
Erik
if you cant seem to get rid of the rich smoking mixture with just changing the normal jets (main needle and pilot)do a search on the s-8 nozzle i put one in my 2002 cr250 and if made a huge improvment i live at sea level and run pump gas even with the s-8 nozzle you will still have to rejet but at least the bike will respond to jetting changes when my bike was stock i tried even the leanest pilot and the bike would still want to foul a plug if you rode the bike at closed -3/8 throttle for just a few seconds
dodgeaspen
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- Dec 11, 2002
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my 02 250 is a jetting nightmare! My spudders and spits on the bottom horribly. My latest problem is that when I start the bike it is automaticly loaded up even after totally cleaning it out it before shutting it off. I'm thinking that this could be possibly the float level and not just the jetting. I'm currently running a 30pilot and a 390main at 0-1000 ft. What kind of oils/ratios are you guys running?
piston eater
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- Oct 3, 2002
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have had no problems with my bike but would guess the choke curcuirt would be open for soom reason
slickpuss
Beef706 helped me alot jetting mine so I would take his advice. The thing I found was you just have to play with the jets one circuit at a time until you fine tune it. I started at the bottom on the low end (this is where this bike suffers) and work your way through. I also played with different premix until it ran good.
My jetting:
Hope this helps. I am also at sea level so that makes a difference. :thumb:
When I first got it I ran like everybody else, Spooge dripping, sputtering, fouling, and everything else you guys said. Now with these settings it runs very crisp right off the bottom and no fouling or spooge. The race gas and premix helped too.
Beef706 helped me alot jetting mine so I would take his advice. The thing I found was you just have to play with the jets one circuit at a time until you fine tune it. I started at the bottom on the low end (this is where this bike suffers) and work your way through. I also played with different premix until it ran good.
My jetting:
- 30 pilot
- 1st clip stock needle
- 390 main
- 2 turns air screw
- HP2 synthetic/C12 VP racing fuel 32:1
Hope this helps. I am also at sea level so that makes a difference. :thumb:
When I first got it I ran like everybody else, Spooge dripping, sputtering, fouling, and everything else you guys said. Now with these settings it runs very crisp right off the bottom and no fouling or spooge. The race gas and premix helped too.
Last edited:
bedell99
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- May 3, 2000
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AS for the S8 nozzle there a quite a few good threads on the subject. It will lean out the bike in the low and middle circuits. The nozzle is also refered to the needle jet. It is what the main jet screws into. The part # for the nozzle is a yamaha part for a yz125 mikuni carb:
3TC-14141-s8-00
I've heard good things about this jet especially for people who run in the lower rpm ranges. It is approximetely $20 and you can obtain it from any yamaha dealership.
Erik
2002 cr250
3TC-14141-s8-00
I've heard good things about this jet especially for people who run in the lower rpm ranges. It is approximetely $20 and you can obtain it from any yamaha dealership.
Erik
2002 cr250
dodgeaspen
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- Dec 11, 2002
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I just ordered an s8 nozzle. I was told to start my jetting at:
400 main, 35 pilot and stock needle in the third position. Anybody agree/disagree??
400 main, 35 pilot and stock needle in the third position. Anybody agree/disagree??
the main sounds about right i run a 410 in the cold temps (40-65)and 390-400 in summer but i bet you might have to still lean out the bottom end with a smaller pilot (30-32.5) and maybe go to the second clip on the needle but try what you stated first and see how it runs
Dodgeaspen, the 35 pilot is a richer pilot. It sounds like you want to go leaner.
A 30 pilot perhaps?
Also get needle 6BEY30-76 Honda # 16206-KZ3-L22. This is a leaner needle and will help get you started in the right direction.
I have messed with all of these needles and jets. By far the best mod I made was shaving the slide 2mm. Cleaned up the off idle performance in a big way. Just a thought.
Good luck and keep us posted.
A 30 pilot perhaps?
Also get needle 6BEY30-76 Honda # 16206-KZ3-L22. This is a leaner needle and will help get you started in the right direction.
I have messed with all of these needles and jets. By far the best mod I made was shaving the slide 2mm. Cleaned up the off idle performance in a big way. Just a thought.
Good luck and keep us posted.
dodgeaspen
Member
- Dec 11, 2002
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The real strange thing about the bike is that when I bought it was bad but now it is even worse. I do a lot of hare scrambles which have "dead engine" starts and when I start the bike to take off it is extremly loaded up. It just started doing this recently. I assumed it was the float height but that is fine. I just hope these mods help!
Have you checked to see if your reeds are chipped, cracked or lifted? This will cause poor performance throughout the rev range but most noticeably at low RPM. Since the bike ran decent and then started running poorly, you need to see what has changed. Jetting won't change on it's own. :confused:
dodgeaspen
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- Dec 11, 2002
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I checked the reeds and float level...both appear to be fine.
