FLAT CR carb jetting general settings?

Hi all... I have a 04 CRF250X model... I have been searching all over the net to try and understand the general rules for a flat CR carb jetting.. most have there own ideas of what runs good at what sea level etc...

Im looking to find out the FACTS /general rules to what jet numbers to use to stay in spec which each other when changing..

Im at sea level in Brisbane , Australia...

1. pink wire mod done.

2. Airbox top cut out..

3. standard exhaust

Some are using a range of MAIN jets between 148-165..

Is there a rule of thumb in numbers Ie, 160 main jet 42 pilot jet, if changed one would the other have to change??

In my bike i have the

1. Main= 168,

2. pilot = 40.(i think its the pilot)

3. one of the Two jet around the main .. 80( carnt quite make out number but looks like 80)

4. There ia also another jet that on the air box intake side, slightly of centre... This one is 100...What is this one??

40,is the pilot.- part of the idle circuit

80 is the starter jet - Used only when the choke knob is pulled

the 100 is the slow air jet works in conjuntion with the pilot jet and fuel screw. Is nearly never changed.

Jets are only changed to resolve a particular problem.

You change jetting when:

You make a substantial change in air pressure (altitude)

You make a minor or major change to any intake or exhaust.

Stock jetting is fine for a stock bike

If you uncork it you will need to change the jetting.

Go read the pinned FAQ;s in the 250X forum.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Jturn
      38MM Cast SmartCarb. Purchased a couple years ago for a yz250. Don't have the bike anymore, and it has been sitting around for about a year. Used, but in fine working condition. You can also purchase a different needle for different bikes, as well as rebuild kits from their website.
      Asking $250 shipped to continental United States. I can arrange other shipping options at the buyers expense.
    • By faizakhtar125
      Hey guys I just bought a bike last night. So the seller said the bike will turn on but then die. We didn't try it because it was really late at night and it was raining (seat was wet). But he said if you bump start it, it will turn on and ride. So what do you think the problem is? I just want to make sure it runs... I probably won't be able to bump start it till Saturday (rain)... It's a four stroke, and I know absolutely nothing about them. Thanks.
    • By knotduke08
      I know this topic has been discussed in the past, but I have not found any options available for the new 2018 bikes. I live and work for a new Beta Dealer (Auburn Extreme Powersports) in California, and we are having a difficult time mapping the RR-S bikes for full FMF exhausts. We have tried contacting Beta Support several times for this issue to no avail, and we typically are given the runaround when transferring to techs and secretaries. From what we can gather, the FMF flash is designed for the RR bikes, but not the street-legal counterparts. Every time we try to install the FMF map onto an RR-S errors occur, and the programmer screen goes virtually blank. We have heard through the grapevine that some are using the RR maps on the RR-S with success, but we have yet to try it, even on our own bikes for fear that it will permanently erase or damage the CDI. Any and all help or suggestions regarding this topic would surely be appreciated! Thanks, Ben.
    • By husky159
      I have the following to sell...
      215 grip studs with the insert tool. Only 2 rides on them. $70 + shipping 
      Stock 17’ 300xc silencer with enduro engineering spark arrestor. (Small dent, a few scratches) $70+shipping 
      hyde skid plate for 17’ 300xc in good shape just your normal scratches. $60+shipping
      mikuni 40mm carb with 2-3 rides on it. Includes throttle cable/ tube. Also extra jets and such. $175+shipping
      feel free to ask for more photos
    • By Charles Mrizek
      This replaces the tube that connects the two carbs on a 1987 Honda XR600R (it may fit other years). 
      Made in the USA. 
      Constructed of TPU  (solvent safe plastic.)
       Its durable stiff abrasion resistant yet flexible enough you never have to worry about breaking it when you're taking apart your carbs. 
      Fits the o-ring perfectly and slips into the carb nice and tight.
      Matches the rear shock coil. 
      If you would like to buy one contact me via e-mail. They cost $20 Shipping is free (anywhere in the USA). $10 off for active duty or retired military.
      Make your subject: XR600r