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2009 yz250f (5000 ft elevation) what jetting?


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i just put a FMF power bomb header with a lexx slip on and i was wonder where to start on jetting before i ride. from fuel screw , main jet, pilot jet. right now i have stock jetting with motor stock and stock air filter. the full exhaust was the only upgrade. i live in albuquerque, new mexico and ride between 4500 to 5200 ft elevation. any suggestions.

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I also live in Albuquerque. I have a full Ti 4.1 with a Mega Bomb. I'm running the JD jet kit, so my jetting will be different. My riding buddy has an 09 YZ250f with a Power Bomb and Power Core slip on. These are his jetting specs, his bike runs great with little backfire.

Pilot; 42, I have a 45 in mine, with the 42 the idle does hang a little when letting off.

Fuel Screw; 3 turns out

Needle; (stock 2009) @ 4th clip

Main; 178 (stock)

Leak jet; 80 (stock) I run a 60, gives it just a little more down low.

Saftey wire the accelerator pump.

My buddies bike runs great with these setting.

My setting with the JD Jet Kit are as follows;

Pilot; 45

Fuel Screw; 2.5 turns out

Needle; JD Red @ 4th clip (will run blue needle as it gets cooler, and less humid)

Main; 180

Leak jet; 60

Saftey wire the accelerator pump.

My bike runs great with these setting, I don't think it could get much better. Also JD gives you the jetting specs for different altitudes if you ride anywhere higher.

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Saftey wiring the ap is the same as the oring mod, there should be a sticky at the top of the jetting forum showing how to do it. But your using saftey wire in the place of the oring.

We ride all over. SpeedwayMX, Moriarty MX, Cedro Peak, Montessa, Rio Puerco, Rainbow, Jemez, Placitas.

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Saftey wiring the ap is the same as the oring mod, there should be a sticky at the top of the jetting forum showing how to do it. But your using saftey wire in the place of the oring.

We ride all over. SpeedwayMX, Moriarty MX, Cedro Peak, Montessa, Rio Puerco, Rainbow, Jemez, Placitas.

Where in Placitas? That's where I live, (Er, well, lived. I just moved.) but I didn't think there were any legal places to ride. I've ridden the oil pipeline from Placitas all the way to East Mountain High School, but that's about it.

I also frequent Cedro, Montessa, and Rio Puerco.

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You have to be careful when safety wiring the AP linkage. Not every carb can handle it.

After you wire the linkage together, you have to check it to ensure the AP diaphragm does not bottom out. If it does, you can break the black plastic link. You will also have to redo the wire and recheck for binding if you adjust the AP timing. Because the oring can be installed in only a minute or two, it is a safer way to go. Prophylactic replacement ensures no broken orings during a outing. Or the best 'fix' is a stiffer AP spring like offered from Merge Racing.

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went good, didnt have to re jet at all. thanks for the replys.

FYI, it may have ran, but did it run at it's peak? When we go from Austin TX elev 600'ASL, to CO, elevation 9000', we drop the pilot 1 size and the MJ 2 sizes and move the clip all the way lean. Our initial day of riding, we had dropped the PJ 1 and MJ 2 but were off on the needle. Once we moved that, bike ran much better.

I'm suggesting that you do some testing as you might like the results much better than what you've got.

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