I read in one of the recent posts about the early B-40's being less powerful than later versions, and the way to tell was that the piston had half circles cut out of the piston skirt. I checked the one I have and it is the older model. While inspecting the engine further, I discovered that the piston at BDC completely masked the front and rear ports. So my guess is that relieving the piston skirt, on the later models, is the reason for the additional power. My question is, does anyone have an late model engine or piston available to confirm this, and to measure the amount of material that has been removed from the skirt? I can make an educated (?) guess, but it's always nice to know what the manufacturer did.

HI Pete,
Thanks for the input, it's what I was looking for.  I was pondering because of a thread I read here but was unable to relocate. In any case, it mentioned a difference in the old and the new B-40 power wise, and as I was cleaning the one I had,  I thought it might stir some interest to bring up the skirting issue I had noticed. Maybe I should blame it on the long Michigan winters; too much time to think. I wrote that after another 4 inches of global warming had just dumped on us, and an unknown amount of freezing rain turning to snow is forecast for tonight. Oh well, think spring.
Al B.