'03 CR250 How will it run with this jetting?

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I_Duddits

Member

May 5, 2008

4

0

• May 11, 2008

• #1

So the bike I've been toying with was a freestyle bike. I've rebuilt the top end and she runs but not as strong as a 250 should run in my opinion (a subjective thought I know, how do you know "without riding a few of them" if she's running right or not?

So I stripped the carb, the jets in there are a 30 and a 633. The bike has an FMF pipe and PC silencer, Cylinder is standard.
Seems 633 is pretty damn big, how would this setup perform in terms of power delivery? Is this setup normal for a freestyle bike (Being as most od the airbox is cut away to make way for grips/ Most od the riding I do is logging roads.
What size jet should I be running in there with an FMF pipe? I'm at sea level BTW.

 

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hadleycat

Member

Feb 12, 2006

16

0

• Jun 4, 2008

• #2

I have an 03 cr250 with a fmf fatty and shorty silencer, V force reeds. My jetting is 400 main, 40 pilot, 38-70 needle, 1 st clip. also s-8 nozzle. I run torco 110 fuel, bike is very crisp and responsive I am in mich. at 600 feet. this is the best set up I have found for this bike. I also run a ngk br9eix plug. I dont think a 633 is a jet size for the stock mikuni carb. I beleive mxa mag. website has a write up on the powervalve cable.

 

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steve.emma

Member

Oct 21, 2002

285

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• Jun 4, 2008

• #3

im at sea level and i run a 390 main and a 27 pilot with the leanest honda needle, bike runs well. that number you quote cant be the main jet size, you must be reading it wrong i think.

 

mx547

Ortho doc's wet dream

LIFETIME SPONSOR

Nov 24, 2000

4,784

103

• Jun 5, 2008

• #4

just replace the piece of crap mikuni with a keihin and forget about carb problems.

 

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hadleycat

Member

Feb 12, 2006

16

0

• Jun 5, 2008

• #5

I love the mikuni on mine

 

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steve.emma

Member

Oct 21, 2002

285

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• Jun 6, 2008

• #6

I love the mikuni on mine

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ditto. ive not had any problems with mine.

 

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Todthebod

Member

Nov 3, 2007

9

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• Jun 8, 2008

• #7

about 1200 above sea level and 80 degree temps, I run a 400 main, 32.5 pilot and I don't know what needle but it's probably a lean needle in the 3rd position. I also have a cut airbox and it didn't affect my jetting at all.

 

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SQUIRLEYMOFO

Member

Jun 11, 2002

310

0

• Jun 11, 2008

• #8

steve.emma said:

im at sea level and i run a 390 main and a 27 pilot with the leanest honda needle, bike runs well. that number you quote cant be the main jet size, you must be reading it wrong i think.

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I'm at a 27pilot,380 main and I just bought a S-4 nozzle.....I hven't ridden it since oh and I'm at about 1500 ft above sea level. I've tried both carbs now I back to the stock one.

 

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steve.emma

Member

Oct 21, 2002

285

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• Jun 12, 2008

• #9

hey SQUIRLEYMOFO what do you find with the different nozzle's effect on the jetting? what i mean is do they just work with the needle to alter the 1/4-3/4 response? or is there more to it than that. im still running the standard nozzle (s8 i think) but havent really had a reason to change it. also where do you get the part numbers for the different nozzle's?

 

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helio lucas

~SPONSOR~

Jun 20, 2007

1,020

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• Jun 12, 2008

• #10

this is what fmf recomends for your bike:
400 main
needle 38-70 in 1st position
air screw 1.5 turns from full closed

but i think they jet the bikes from stock form only with fmf exhaust. so your main may look to big, but if the bike is changed in some way it may be the correct one...

for that size of main i would supose your bike was runnig some kind of alchool (just a guess)...