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Just picked up an '05 YZ250, have some jetting ?s

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Hi guys, I'm new to this YZ forum, spend most of my time in the Northwest section. I just picked up a '05 YZ250 (used). It's in really good shape, but it has some jetting issues. I'm very familiar with jetting, got my '02 KTM 300EXC dialed in, but am not familiar with the yamaha jetting specs and such. Right now the jetting is as follows, 185 main jet, N3EJ needle w/clip in 3rd pos., 50 pilot jet, and a #7 slide. Seems awful rich, especially when it will be all woods riding from sea level to 6000ft. Is there any special needles like maybe the JD Jetting needles or single taper needles like the DDK, CEK, etc. Was thinking about getting some head work done also, so I can run race gas (VP C-12) which is the same gas I run in my KTM which is had head work done to it. I would like for both bikes to run the same fuel to keep things simple. I would really appreciate any info you guys can give me concerning the jetting and maybe possible motorcycle guros who are familiar with head work on Yamahas and porting too. Also will be adding the Rekluse auto clutch and possibly a flywheel weight.

Thank you

Little Jeff

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I now have an 06 125/and 250 but i live and ride around 5500-6500 and these were the jetting specs I used

5000-6000 elev

170 main

50 pilot jet

2nd clip

dont remember air screw

8000-12000

165-168 main

48 pilot

2nd clip

those are ballpark to help you go. Sounds like your main is set for sea level. I think I used that at Glamis Sand dunes.

If you are interested in a trick Shark fin by Zip-ty I will practically give it away. It fits only the 05 and changed for 06. PM me if interested. I have pictures, info.

Have fun with your new bike. I used the bike for trail riding, desert play riding, whoops and sandwashes, and races in USRA Utah desert series with all stock gearing. I did not really do much other than change jetting for my elevation and loved it.

good luck

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I'm in N. Oregon and ride at approx.1500ft. For this weather I've ended up w/ 176mj, 48pj, needle #2 slot and air screw 1 1/8 out. Bike flat rips!

I've ran this jetting with straight 91 octane and with a 40/60 mix of 110 leaded and 91 octane (both w/ Amsoil @ 32:1).

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Do you like the race gas? do you notice a difference? the only difference I have noticed with my buddies "done up" bike on race fuel, is that he is always fixing with it and never happy with how it runs....really finicky! I race my bikes in HS and XC with premium pump fuel and they are clean and crisp all the time after some jetting when I first own the bike.

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I really like VP C-12 race fuel. Kind of spendy but worth it to me. I also think it makes the jetting easier than with pump fuels, IMO it is a little more consistent than pump fuels from batch to batch. Just put a little leftover c-12 in my bike today after I cleaned the carb and put some smaller jets in it, a huge difference. Bike is scary fast! I'll tweak it a little more though.

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I run 93 octane with Bel Ray HR1 at 32:1...the bike runs flawlessly. Stock jetting with the exception of the needle being lowered one notch...(Dallas Tx elevation 620ft)

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Do you like the race gas? do you notice a difference?

I cant tell any difference at 40/60 (110/91). I'll use the remaining fuel and then back to a strict diet of 91.

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