What everybody has said here. I’ve got cans that have gas from years ago between the boat, weedeater, lawn mower motor cycle etc. I keep a little shy of 20 gallons on hand and cycle through it first in first out. That run just fine in anything I put it in. The 2 cycle mixed gas is the worst offender as I use so little of it it might take me years to make it through a gallon.

That said three weeks is nothing. The gas I put in the chainsaw two weeks ago had been in the can since the last administration, and it cranked up and ran without fail for hours, the only time it quit was when it ran out.

There’s two things that could get it acting right that I can think of: Replace the cylinder (expensive, may not work but might) Shim it i.e. find a washer with internal diameter of cylinder pin or smaller and rut it out to the right diameter, then file it down to the width that takes the play out ( couple issues with this, one it’ll increase the flash gap i.e. bigger halos, reduced velocity and increased leading, two potential annealing of the makeshift shim with the fram of the gun) Let us know how it goes

Seconding this one. Looking at the furthest from camera case, my money it that there is play in the cylinder along the axis of the cylinder pin. That case being swollen, just above the rim means one thing, that the case has enough room to move back out of the cylinder while firing to allow that to happen. Overpressure i.e. hot loads may be contributing to an issue you wouldn’t observe with lighter loads. Have you played around using different ammo?

“la forma de la nalga”

Whay they 👆 said, have fun. They’re a pain in the ass to get rid of.