quick help please, jetting a 2001 CR250


jdager

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Apr 26, 2008
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Hi all,
I just bought a new 2001 Cr250, and it has been nasty weather lately, so I havent got to ride it much except up and down the street. in doing so, I noticed that there seemed to be considerable bog in the lower to mid rpm range, then hits the band hard. I have herd these bikes can be tricky to jet, so I was looking for some help. first of all, anyone have any tips and tricks for getting the carb out of the frame? I worked with it for a while, and getting the throttle cable unhooked seemed to be a huge pain. anyway, I checked the jets, and I have a 400 pilot, and an s-9 slide I think it is called. havent been able to check the pilot or needle position yet. I am also not sure which screw is the air screw, is it the tiny brass one, with a locking nut around it? I am looking to do mainly woods riding, and the bike has a fmf sst pipe and silencer. my elevation is about 1000 feet, and the average temps now are about 30 degrees. if anyone can give me some pointers on how to get close, so when I go and jet it myself, I am close to where I need to be, that would be great.
thanks in advance,
Jim
 

Shaw520

Damn Yankees
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We charge more for the quick help,...... as opposed to the regular speed help. :nod:
 

Matt90GT

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May 3, 2002
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I have not jetted a CR250 in a long time. My best advice is do a plug chop, inspect the plug and see where you are at.

If that is beyond your capability or you just want a better jetting setup easier, get a JD jet kit for the bike.

www.jdjetting.com
 

jdager

Member
Apr 26, 2008
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anyone have any experience with the s-7 slide? I have read some about that and people seem happy with it. any idea where I should start out with the rest of my jets to get me close?
thanks,
Jim Dager
 

00KX250Byrd

Member
Dec 15, 2007
27
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Jim,

As Matt said do a plug chop. Warm engine, Ride at WOT, and hit kill switch.
Plug should be a tan color below electrode. Pull your carb, remove pilot and main jet, read number on them, and go to your dealer and buy some jets, 2 lower and 2 higher.
Also, check where your needle clip is set.

Britton
 

moto9

Member
May 5, 2004
14
0
The best and quickest fix on the stock carb is a JD jet kit...the kit will get you as close and any mix of trying a pile of jets, slides etc...

Some bolt on items will help with gaining back low end:
Flywheel weight, I went 13 oz for the tight, greasy, rooted, hilly, jungle stuff I ride.
V-force or rad valve
torq spacer
air box mods
Gnarly pipe, shorty silencer
36mm carb (some loss of top end)...use a 00 air boot
slight adjustment (retard) of the stator
1 up on the rear sprocket
after that it's porting and head work.
Don't forget suspension....I hated my CR until I got the boingers working
Hope that helps
 

James

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jdager said:
Hi all,
I just bought a new 2001 Cr250, and it has been nasty weather lately, so I havent got to ride it much except up and down the street. in doing so, I noticed that there seemed to be considerable bog in the lower to mid rpm range, then hits the band hard. I have herd these bikes can be tricky to jet, so I was looking for some help. first of all, anyone have any tips and tricks for getting the carb out of the frame? I worked with it for a while, and getting the throttle cable unhooked seemed to be a huge pain. anyway, I checked the jets, and I have a 400 pilot, and an s-9 slide I think it is called. havent been able to check the pilot or needle position yet. I am also not sure which screw is the air screw, is it the tiny brass one, with a locking nut around it? I am looking to do mainly woods riding, and the bike has a fmf sst pipe and silencer. my elevation is about 1000 feet, and the average temps now are about 30 degrees. if anyone can give me some pointers on how to get close, so when I go and jet it myself, I am close to where I need to be, that would be great.
thanks in advance,
Jim

To get carb out of frame:

1. Loosen carb-intake and carb-airbox bands
2. Rotate top of carb towards you on left side of bike
3. Remove two screws on carb lid and pull it off along with pulling slide out of carb.
4. Retract spring and retainer ring and manuever throttle cable out of carb slide to get to 6mm bolt that secures needle
5. Rotate top of carb away from you to access float bowl, main, pilot, and nozzle.
6. If you want it "out" from here, you can wrestle it out of the intake/airbox boots or raise/remove the subframe.

Sounds like stock jetting and you probably have the 35 pilot. The 400 you mention is the main and the S9 is the nozzle.

The air screw is the tiny brass colored screw to the lower rear of the one with the locknut. The one with the locknut is the idle adjust.

For the temps you mention, my guess is the bike is too lean. You would need to adjust the idle screw and change pilots to get rid of that low-mid bog. I wouldn't be surprised if the bike ran better with the needle raised one notch and a 410 or bigger main at 30 degrees. I know my bike required some big changes last time I rode in weather any where near that cold. I doubt a plug chop will be helpful on your low-mid jetting. Be careful about running WOT to plug chop in 30 degree weather unless you KNOW your main jet is big enough. You don't want to seize the engine.

For normal temps 70-90 degrees, I think I generally have a 32.5 pilot, 390/400 main, needle 2nd/3rd clip, and a S-7 nozzle.
 
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jdager

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Apr 26, 2008
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well, got the carb apart to check jets, and had a 30 pilot, 400 main, needle on second from top clip, havent checked air screw yet. what should I run to hopefully get rid of some of the low end bog, but more importantly keep from running too lean on top? thanks James, that was really helpful. one question though, when I loosen the boot retainers and try to rotate the carb, towards me, the throttle cable is too tight to let it rotate enough to get at the screws on top. any ideas on how to get around this, or am I just being an idiot?
thanks,
Jim
 

James

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Check to see how the throttle cable is routed. I run mine outside the head stays on the left side. I have to remove the top to get to the bowl this way...but it alleviates the tightness which eventually breaks your outer cable sheath from turning the carb. You may have to take the throttle or tank and head stays off to remedy if the cable is routed up the middle.

If its that cold, I would start with air screw at 1.5 turns, 35 pilot, needle in middle clip, and adjust your air screw in the direction that seems to improve until you reach one turn out one way or three turns out the other way. If you reach 1 turn you need a bigger pilot and 3 turns out means smaller pilot. I have a hard time noticing air screw changes sometimes and it is often easier for me to just try a different pilot leaving the air screw set in the middle. Since 35 pilot was generally rich on those bike in normal temps, I don't think you will need to go bigger than 35 especially if you get the needle and main richened up but it is possible. I'd also keep a 32.5 on hand for slightly warmer temps.

I like to start with the low circuits and work towards the main jet...just my preference. I think the main is "ok" at 400 to dial in low range as long as you dont run it wide open for any period of time but could put a 410/420 in there to be "safer." It's possible 400 is right or it could need a 430 or more...hard to say without riding it. If it feels like it is running tight at WOT, try a bigger main. If you keep going bigger on the main you will feel it change from tight to perfect to kind of rough until the point where it starts bogging the other way or loading up. Do this enough and you will get a feel for it. Even if you get the JD kit or a Keihin carb (always comes up) you will still have to know how to adjust them if your temp range is 30-90+ degrees.

I have the answers to your fork fluid questions also but I want to check my book when I get home to be sure. I think it is 6.5 ounces in the inner chamber and 11-13.9 outer with standard being somewhere around 13.

Not an idiot..we all learn somewhere. Took me a few broken cables, a seized engine, and some foul language to get it down to psuedo science.
 

jdager

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Apr 26, 2008
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James, thanks again for your detailed description. the bike seems to be loading up in the lower rpm ranges, until I get to about half throttle, and then it seems to clear out some (but I havent rode it much since it has been so stinking cold this week). also, my biggest fear is that I have never had a bike run lean, and I dont know if I would recognize it, or just keep running it and accidently seize my engine. all my bikes, if they were gonna be off, they were rich. also, when I rode it up and down the street yesterday, when I would come to a stop and let it idle, some times it would start to idle up really high, but if I flicked the throttle, it would go back to idleing normally. it didnt do it all the time and would sometimes idle just fine. it almost is like the choke is on. does this sound like it is getting lean, or does it sound like the throttle cable is pinched?
thanks,
Jim
 

James

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I am still guessing lean.

You can check if the cable pinching by testing throttle twist/return especially when bars are fully turned to the stops.
 

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