BRUCE, I do the same thing all the time, and it is usually with something like a tap. The other day I was [ahem] POLISHING the crank in my PAW 15 with a carbide rotary file. To get adequate reach I didn't have the tool in the collet all the way. After my "polishing" was almost done, I went back in to hit one more spot, the tool bit grabbed, spun the crank out of my hand and sent it rocketing across my barn into the abyss of saw dust, scrap metal, garbage cans, tiers of shelves, etc. I actually had to clean the place up and I found it 4 hours later in the bottom of a bucket full of left over framing brackets, with out a scratch on it. The crank work, and a little "polishing" on the top of the exhaust port should allow me to run with the big dogs in 70mph DBAT and then switch back to a smaller venturi for 65mph NOSTALGIA DBAT. Oh, the other thing I "noticed "while the engine was apart, is there are a couple of half round notches on the piston skirt now, and you can see into the crankcase when the piston is at TDC. WE're going to go at it this Saturday in SEDRO WOOLEY, WA.