have a 2007 WR450f w/ Leo Vince exhaust which I run with baffle in place. Have done all the prescribed WR450f carb/jetting mods and bike runs great. On a whim I removed the baffle to see how it would run. Ran like crap. Off idle was OK but at RPM's it coughed and sputtered. Furthermore, I couldn't even get the bike to die at idle when I turned the fuel screw all the way in. With baffle taking the fuel screw all the way in will choke it and you can go through the ritual of backing screw out to find happy strong idle and good mixture.


1) Why does bike act like it way too rich when baffle is removed and tampering with fuel screw? No other variable is changed.

2) Why is whatever is causing this not affecting off idle performance and only coming into play at higer RPM's.

Seems like if you remove restrictions on exhaust by removing silencer/baffle it would show lean characteristics not rich which, if I'm not mistaking, is what's going on with the fuel screw adjustment result.

turn the idle down as low as it will stay running and redo the fuel screw test.

That's the problem. I can't get it to stall with the baffle out. Only with the baffle in can I get the RPM's to fall down so I can bring it back up. With baffle out revs don't fall off even with screw seated full in. How can this be?

did you turn the idle speed down like i suggested?

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