05 WR450 surging issue

Have recently encountered surging with throttle off either at idle or backing off at speed. It seems to be getting worse by the day (have to keep my finger close to the kill switch). It starts O.K. and will idle after warmed up. Have checked venting, fuel flow, float level, throttle cable, spark plug (good color). This bike was running fine until recently. It is if a shot of gas is getting past the carb. after backing off the throttle. Have checked for vacuum leaks on carb. but nothing found. The bike will not start when hot until I pull out the choke completely and push it back in. Any clues?

my guess is your jetting is off . mine surges bad at mid thottle until I get the jetting right. try putting your needle down a clip , and see if it gets better or worst. it could also be dirt in your carb.

Thanks for tip of dropping the needle down a notch. It worked, thanks!

FYI - Jetting does not suddenly change. I suggest you look for the cause.

Based on lowering the needle a position leads me to think the needle jet emulsion tube is worn. This causes the bike to be richer and you lowering the needle, leaned things somewhat. I suspect if you very carefully inspect the tube, you'll find the hole is slightly oval.

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