You can't 'tune out' a mistake like exhaust...
You never want to run a straight pipe a on a 2-stroke, and why you are having issues.
2-strokes don't have valves.
You are literally spewing power and raw fuel out on the road when you ride!
Follow the green fuel in this vid.
With a strait pipe all that green gas/air/oil mix escaping the engine just goes out the end with a straight pipe and on the road!
An expansion chamber like the one shown has a back-force wave timed to shove the fuel mix back in just in time for firing for a bigger punch and more power, not to mention no more puddles of oily fuel on the ground wherever you park.
Okay, yeah, I understand, I think, about the back pressure pushing some of the exhaust/unburned fuel back into the combustion chamber to mix it with the next shot and all at least I think I explained it right. But my newest pipe that I welded up has two opposing 90 degree angles in it. Shouldn't that help a little? But what I understand about 4 stroking is that the engine is not scavenging all of the exhaust out of the combustion chamber for a new clean shot of fuel/air. Am I wrong? Sorry, still new at this.
And just so you know there are no puddles of fuel on the ground where my bike sits overnight. I even bring it inside the house overnight. Also, It seems to run a lot better after it has warmed up a bit. Still four strokes but not as often when it's cold.
The stock pipes do an OK job of producing back pressure to shove the unburnt fuel back in the cylinder, but a tuned expansion chamber exhaust does it much better, it works like a reverse turbo charger and gives you the best power boost and my #1 rated single upgrade there is for a 2-stroke engines.
That should set ya on the right track ;-}