Problems Linked or Not

I have two problems that I need help with. My engine is stuttering at 1/8 to 1/4 throttle and I'm burning a little oil. Any help with each problem or a combination fix?

The engine stuttering, I thought was a jetting issue when I went on an out-of-town ride, but now the bike is at home and I still have the problem. At higher throttle, everything sounds and feels fine. After this weekend's race, I noticed some black soot around the exhaust. I have the JD Jet kit and jetted to the recommendations. Today, I played with the fuel screw and the bike still ran with it turned all the way in. I changed the air filter and had the same results. The bike used to run fine and I didn’t make any changes.

While I hovered over the bike this afternoon scratching my head, I checked the oil on the dipstick. It was low so I filled it back up to the right level. I needed to add 200 milliliters. I have about 7 hours of riding since the last oil change.

Do I have a problem or problems? What do I need to do?

Hi,i have just spent a week getting my jetting sweet and to me it sound like you are running a bit rich on your needle and luckily its the easy to get to i didn't have to take my carb of to do mine on my 02 426 ,just took tank and shrouds and seat off undid the clamps and spun it toward the shifter side the is only just enough room to get the Allen key but it worked then used pointy pliers to pull the needle .

Try one or two clips up on your needle if that doesn't work pull the carb out and give it a good clean .

Also check the fuel scew still has its o ring ( that little trick got me good )

What bike is it?

If the jetting is too rich, will it burn oil? I know how to jet the needle, fuel screw, and the main.

I have a 09 YZ 450F.

Thanks for the help.

Also check the fuel screw still has its o ring ( that little trick got me good )

Yep. I was running rich. The O-ring was cracked. What really sucks is while I was fishing out the O-ring, I dropped the washer that goes between the O-ring and the spring ... and I can't find it. I spent an hour searching a 10-foot radius.

The washer is PN 3TJ-14952-40-00 from Yamaha. The O-ring is 3TJ-14562-40-00.

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