2009 crf250r jetting

Well, based on what you have said, I can see why you are having issues.

You should only ever change one thing at a time and test.

The main jet doesn't effect quarter to 3/4 throttle. that's needle.

Neither needle or main effect idle, that's pilot.

So, get the idle sorted out, then move to mid throttle and then once that's right work on your main jet.

your sudden erratic idle after moving the needle could have been an accidental bump on the float?? needles dont affect idle. go back to the stock jetting and start over. 3 turns on the screw tell me you need a smaller pilot

3 turns on the F/S means you need a LARGER pilot jet, which is very common on stock 4 strokes. Go up one size and set the F/S to 1.5 or 2 turns to start with. Once you get it running go warm it up and then turn the F/S in until the idle breaks up, then back it out until it smooths out, this will verify you have the proper jet. If it doesn't respond to input on the F/S it's too rich and you'll need a smaller jet. Once you get to this point you can go ride it around and fine tune the adjustment for best response, this should be within a half turn or so from where the idle smoothed out. Then do the main jet as it effects the volume flowing over the needle. Best way for most people to do the main when you have a 30 dollar spark plug you don't want to cut up is to just swap it out and use the butt dyno to see if pulls harder. The main takes about 2 minutes to change in the CRF. Warm it up and run it wide open through the gears a few times. Quickly go change the main a couple steps in either direction and you'll be able to feel if you're helping or hurting. No worries about going a little too lean while testing. Once you've got the main set you can play with the needle, which sucks to work with. My CRF was very responsive to needle clip position. I also did a few accelerator pump mods and ran a 45(I think) leak jet to clean up the throttle whack response. Timing, duration and aiming of the squirt are also important. Good luck and let us know how you make out!

_JOE_ said:

3 turns on the F/S means you need a LARGER pilot jet

Click to expand...

whoops....what he said^^^ :cool:

If Honda changed part numbers, interchanging can get very scary $$$$.$$ With new parts laying amuck, why bother going down the wrong road? Vintage Bob

I seen the top end in my 74 Johnson 33 hp boat motor. 50:1 and an inch of rings on each piston? That will get fixed this winter. A nice 6 hour top end job?