250-500cc 2006 wr250 sometimes gets stuffed up

So I've got a weird thing with my bike, sometimes she gets stuffy & needs to clear her throat...


2006 wr250 with a ton of hours (regularly 80+ a season, had it for 6? Years, many top ends & maintenance)
She's not pretty & def not 'barely ridden' but I try to keep her in decent shape.

Full fmf exhaust (gnarly pipe & turbinecore silencer)
Lectron carb
Piston about 40? hours ago, don't exactly remember

New England tight singletrack rider. I ride aggressive, but tend to ride a gear high & lug it


Most times I'm happy with the way it runs, crisp down low, pulls hard & clean, just like it should
But every so often (usually in real aggressive riding, like a hare scramble) it seems like someone simultaneously stuffed a rag in the exhaust & punched a hole in the pipe, the bike will have a sudden, noticeable change in tone & not want to go anywhere. I know I run it low rpm sometimes but I don't think there's any reason it shouldn't light right up & go in 2nd or 3rd gear at any rpm. If I pull the clutch in while this happens and really ride it like a 125 (lots of gas & clutch work) it will get on the pipe and go, but it doesn't seem happy.
Then, just as sudden as it starts running like that, it will go back to running the way I like.

Top end of the powervalve assembly looks ok, it starts & idles well with the lectron, no bogging when it warms up, sometimes it surges off throttle but not bad I don't think.


What's going on?
I'm wondering if the centrifugal for the powervalve is old & tired? Maybe is hanging up & occasionally not opening, or is staying open? Electrical or fueling? I would think it would be more consistent if it was an electrical or carb problem? It seems load & intensity related. The change in noise is quite noticeable. The silencer isn't in the best shape, maybe it's coming apart internally? I just repacked it last week with no change in performance

the cheapest and most suspect part of any dirt bike is the spark plug, do that first always
the spark plug and actually the whole high voltage system has it's greatest strain during acceleration, I don't mean it actually works harder it's taxed harder
but number 2 is look at the powervalve

I'm ashamed to admit how old that sparkplug is... Good call, she's due for a fresh one anyways

The noise change is interesting, is the pipe sealing starting to fail, between the cylinder or muffler, shouldn’t cause a major power issue though. Got the same bike sadly sans lectron , haven’t experienced this with the maligned mikuni. Please let us know the outcome Wheelie.

Perhaps the reeds are starting to fall apart?