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Looking for jetting suggestions with big bore

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I'm putting in a BBR 240 kit and am hoping someone can offer suggestions for jetting. I have a EvoX full system, ride at 800 ft elev, 80 degree temp and 60% humidity.

2003 CRF230F with power up, current jetting 122 MJ, 45 PJ, 3rd clip.


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I can't tell what it should be but a good methodology is to put MJ in that you know is to big. This protects the bike from getting damaged.

Then work from the bottom up.

Start with the 45 PJ start about 2.5 turns out on the PS.

Get the bike warmed up to where the fins are hot.

Then follow these steps to get the PS set (quoted from http://www.thumperfaq.com/jetting.htm )

Setting the Fuel Screw / Pilot Jet "by Ear"

1. Adjust the idle with the black knob until it is too fast. Then adjust it back down until it is around 1900-2000 RPM or if you don't have a tachometer (see below) until it sounds just a little high.

2. Before you start adjusting, count the turns required to tighten it up lightly.

3. Then start the bike with the slightly elevated idle and turn it out 1/4 turn, 1/2 turn, 3/4 turn and so on until you get to 2 turns. Listen for best RPM and best response to a quick 1/4 turn tweak of the throttle at each position of the fuel screw.

4. Now turn back in 1/4 turn at a time doing the same thing. By now you should have been able to distinguish the speed of the idle and the responsiveness to tweaking the throttle.

5. If it gets better between 3/4 and 2 turns out, set it at the best location and leave the rest of the pilot circuit alone.

6. If it is getting better turning it in or is best less than 3/4 turns out, replace the pilot jet with a smaller one and go through this procedure again.

7. If it is getting better as you turn it out or best at more than 2 turns out, replace the pilot jet with a larger one and go through this procedure again.

Then after it idles fine & has good throttle response on the bottom . Check the needle circuit(haf throttle). Adjust the needle clip as necessary.

Then start swapping MJ’s till you find the one it runs best at.

Also with the stock carburator which is on the small side it's going to pick up fuel real well. High speed air creates greater pressure drop which picks up & atomizes fuel better. So, the sizes may not go up as much as you would expect. If you go to a larger carb you'll need a to rejet with larger MJ at least.

Good luck & have fun with the torque monster!


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