sputter/misfire after extended periods of WOT

sputter/misfire after extended periods of WOT
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I just swapped an 81 jet into my stock carb after shortening the hose to the length as specified by ronk. bike feels a bit weaker in the midrange but carried power much higher into the RPM and picked up mph overall. about a day after this it started to develop a random sputter/misfire but only after about 20 minutes of 35-45mph riding. usually in the 8400-8600rpm range getting up to 9600on some downhills and dragging down into the 7400 range on uphills.

is this the result of it getting hot? clogged jets? the new jet has only been in there about 2 weeks and has about 150 miles on it.

38/81
TVR intake shortened to just the 45* elbow as suggested by ronk
Yoshi exhaust
NCY CDI
Polini Variator with 5.5g sliders
under 200 miles on a new bando belt.

My first thought is to check the jets. Both for cleanliness but also that they’re tight. If they come loose they can cause issues. Also, an 81 seems a little high but if it’s running good I’d stick with it.

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Check the coil wires are good connections and the ground it good as well. Is it stalling out or like popping

I know this is an old post but I would try a 78 jet if things get worse then try an 82 jet.

I’ll bet the 78 will work best.
Also do throttle chops to see how the plug looks.
At the point is starts to sputter/misfire hit the kill switch without changing the throttle. Then pull the plug and adjust the jet size depending on how the plug looks.