backfires/shoots flAMES

Hey whats up? I have a 98 yz400f and ever time i hit the gas then let off it backfires and shoots flames. Do you have any idea?:worthy: It also bogs when throttle is hit very fast, but not when you roll on the power

What a great way to hold off would be passers. As long as you hole shot you should have the finish locked up.

So these issues are due to the carburetor?

I have a buddy who has a WR450, if you whick the throttle when the bike is cold it will shoot a 1'-2' flame. :worthy: After it is warmed up, no problems. Only mod is a FMF slipon.

I just checked the idle set screw and it's adjusted all the way in just so the bike will idle. Is it becuase its jetted wrong?

Yes, your jetting is wrong. From what you have said so far, it sounds like your pilot circuit is too lean. You need to turn the fuel screw out. If you get the fuel screw out 2.5-3 turns and it still has this problem then you need to put a larger pilot jet in.

So these issues are due to the carburetor?
Or an air leak in the exhaust, like I said.
I just checked the idle set screw and it's adjusted all the way in just so the bike will idle. Is it becuase its jetted wrong?

Its turned all the way in to compensate for your clogged PILOT jet!

I don't think i have an exhaust leak cuz i have a dr. d header and silencer. Unless it uses a clamp but i'm pretty sure it doesn't

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