[AzHatch]

Hi guys I’ve been lurking the forum since I bought this bike a month ago, first things first bike specs
Elevation is 5000 ft temp is 80-100
07 CRF250r that I assume was raced
Needle- D551 2nd from the top
Main- 168
Pilot- 42
Float- 8mm
Fuel screw 1 turn out
Uni filter
Dr D full exhaust

So I’ve tried a 40 pilot with a variety of fuel screw positions same with the 42, I don’t have a 45 to try right now. All tests were done at 1/4 turn increments. I have two issues, the choppy throttle at 1/4 to about half, and I’m getting a lot of fuel through the crankcase breather tube into the air box with a decent amount of fuel getting into the oil. Carb has been out, pulled apart and clean a few times so I’m at a loss for what to try next. Bike runs good wide open but choppy in the mid range, I can start it cold with a few kicks with the choke open. When it’s hot it will fire back up with a few kicks and the hot start open. Looking for suggestions on what to try next. I will mainly be doing Forrest service road riding and single track.

[Neekarmic]

I would look into and do some reading on the Accelerator Pump (AP) clean and check it first. Also leak jet. Once you know what you're working with you can go from there.

[Back2-2]

Hello.
1/4 to 1/2 throttle is past the fuel primary circuit. At that point you are into the main jet and needle. I would try to drop the clip 1 position and see how it feels. The needle and needle jet holder could be worn. Hard to check unless you have a pin gauge set but worth taking a look. You did not mention what your spark plug is looking like but worth a inspection after a good run.

The one thing I do not understand is how you can be getting fuel out of the crank case ventilation hose? There should be nothing but crank case oil fumes from that tube and not much oil mist to even see. If you truly have fuel coming out of that tube you have serious issues of way over fueling. That would be so much fuel that it is blowing by without burning and down into the oil and turning to vapor and out the crank case vent. Would probably be an oily thin mess coming out.