I would'nt recommend starting up your shee with that piaece of solder in your cylinder.
What I've done is disconnect spark plug wires , remove carbs, and intake manifolds, then placed a 1 in. length of (1/8 dia.) pc. of solder on top of piston , moved kick starter by hand just to get piston to " squeeze" it , then remove and measure the thinnest section w/ your mikes.
Hope this helps. good luck.