Just picked up an '01 Cr250, Jetting suggestions

Hey all,


Just picked up a nice little 2001 CR250 but the previous owner used to run 20:1 ratio so he had a preset jetting type on the bike. Now, I'm looking to run it at 32:1 ( stock recommendations, plus my other machines run the same mix so it will be way easier for me). I compiled a little table with the current jetting/pro circuit pipe recommendations and reed valves recommendations.


Now my question is, instead of buying every jet in the big gap here and try them all, what would you suggest as a starting point? I currently have only the jets that are installed and no extras so I will have to buy all of them.



jetting chart pic.jpg

Local info:

Ottawa, Ontario, Canada

365ft elevation

will be running in 15-30 degrees Celsius



Should I start with the lowest of every option such as 390 MJ, 2nd clip, 30 SJ?


Now, I understand that jetting is dependent to every bike, I'm simply looking for a good starting point with my two mods( reed valves and expansion chamber/pipe) and I can definitely take it from there.


Thanks for the guidance!

Edited by frank2014

Copy paste didn't work so here is a screenshot of my table

jetting chart pic.jpg

I'd start at 400. Recommended jetting is generally a size or two fat to cover their ass, if stock is 420 I'd be comfortable starting at 400. Then you're probably not going to be running lean and you can go up or down. Or try what you have right now mixed at 32:1 and check your plug and piston wash. If you know how to do jetting you should be able to figure it out man. I'm one of those guys who doesn't like to spend more than I have to, but if you always wanna be making the most power you should be always changing your jets for the temp anyways. I'm pretty sure I'm running a 420 main in my 01 with full fmf and v force reeds but I also keep the same jetting from 5* to 30*C :p
Best of luck, we still got too much damn snow here in Sudbury.

I ride at 100 to 2000 ft and 45-90 degrees(fah) and have used a 410 main, one size leaner needle-3rd clip, and 32.5 pilot. Has been good for me since new. The Honda owners manual has a very good jetting section and chart. I am one of those who really likes the Mikuni.

Edited by YHGEORGE

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 ashfmxuk
      So Been rebuilding my bike and the rubber mallet just "wouldn't cut it"!!!!
      I had to pry managed to sand down it all looked flat but this seems a bit gappy.

      This is only on the outer edge but I can help worry this is going to leak or get shit into the engine.
      Any help or advice would be awesome thanks

    • By Kaito Sutton
      Hey guys, so cant find much online about cr 250r enduro conversions (nothing recent) so im wondering if it is an option or not. I currently have a crf 250x 2009 and a XR 650r. If i want a 2 stroke enduro but want to stick with the honda line up, is a 2007 or 2005 honda cr 250r a good option. and if so what would need to be done to it to get it up to spec for trail and enduro riding. Thanks very much
    • By dirtbikesrule
      If you own a 2 stroke dirtbike,please reply once. Im just wondering how many people on this site have them.
    • By skipn8r
      Note: This specifically applies to the '92 - '01 CR250 engine, but it should be adaptable to any 2-stroke. The basic idea is to pull the carb and exhaust, plug one and pressurize the engine through the other to look for leaks.
      It's very important to pressure test a 2-stroke after it's assembled. The reason is that a 2-stroke gets it's lube through the pre-mix. An air leak means your engine can run lean. Lean means too little fuel. Too little fuel means too little lube. Too little lube means death to your engine. So here we go.
      First, you need to pull the seat, tank, shock, carb and pipe. Everything you need (other than a tire pump) is shown below.

      The assembly below is basically a 1-3/4" PVC plug (same OD as the intake pipe ID) that is transitioned down to a 0-15 psi gauge, a shut-off valve and a Schrader valve (to connect a tire pump). The 1-3/4" PVC plug is a tight fit in the intake pipe, but it'll fit with enough persuasion. I used yellow heavy duty pipe tape (made for gas systems) to put everything together. I don't have all the technical names for everything, but if you take the pictures to a hardware store, they should be able to help you piece it together.

      The item below is an adjustable rubber freeze plug. They are available at automotive parts stores in various sizes, but the closest one I could make work was a 1-3/4" version. You tighten the nut which squeezes two metal plates together which squeezes and expands the rubber piece between the plates. You have to tighten it a lot, but it makes a good seal in the exhaust port.

      Before you install everything, make sure that the piston is at BDC (so that all the ports are open), the spark plug is installed and all other components are properly tightened. Below, you can see the gauge/valve assembly installed in the intake pipe. Make sure to tighten your intake pipe hose clamp tightly as the pressure will tend to push the assembly out.

      Below, you can see the freeze plug installed in the exhaust port.

      Once you have everything installed as shown, use a tire pump to pressurize the engine to 6 - 8 psi, then close the valve and watch the gauge for any pressure drop over a 5 - 10 minute period. A well sealed engine will hold pressure with no observable pressure drop for 10 minutes easily.
      One common "leak" in a healthy '92 - '01 CR250 engine (and probably other types) is through the powervalve linkage. It probably doesn't affect performance, but it'll sure throw your leak measurements off. To avoid leaks, make sure the powervalve linkage is correctly lubed (per the Service Manual) with grease and Moly 60 Paste during assembly.
      If your engine holds pressure with no observable drop for 10 minutes, you're good to go. If the pressure drops 2 - 3 psi or more over 10 minutes, spray soapy water all around the pressure test parts first to check for leaks there. If you find none on the test setup, start spraying the soapy water around the base gasket, head gasket, center gasket etc. Any pressure drop of less than 2 psi over 10 minutes is your call, but I'd definitely fix it.
      I've had really good results by using Permatex Copper Gasket Sealant on the base gasket, PV cover gasket and reed cage gasket. I don't use anything on the head gasket.
    • By ulmanb
      What value would you say a 1986 cr250 with a freshly plated cylinder and new top end, newer tires, newer chain & sprockets, in overall very good condition?
      I picked up the bike (cheap) a month or so ago in need of cylinder replating & top end. Apparently the headgasket blew internally scouring the cylinder. The crank feels good and the bike is very clean/good condition.
      I havent put the bike together yet (too busy to ship cylinder and order parts), but figure I would have a total of $600 (including bike cost) to get it into good running cond.
      A friend wants to buy it as-is for his 15 yr old 200# kid. What value wouldyou put on it in As-is condition vs with a fresh engine?