Personally I believe the 2 mil is a better choice for durability without loosing anything to the very slightly larger 3 mil bore. The 2 mil will have a little better cylinder rigidity preventing distortion caused loss of compression. The 2mil will also have a bit lighter piston reducing mechanical inertia losses, probably will run a little cooler too. Stroker crank street motors seem to wear themselves out quicker than their stock stroke counterparts. The different rod attack angle of the more outboard rod throws side loads the pistons a bit more, maybe not a big issue for a bike thats ridden a 1/4 mile at a time but for a street bike it could in theory mean shorter engine life. The crank pins, on a stroker are welded and re-ground to achieve the offset that gives you the longer stroke. Some of these re-weld, re-ground pins have been known to flake metal and cause trouble. A stroker motor also has to have piston clearences checked at bdc as the piston is pulled further down in the cylinder and could cause the piston skirt to hit the crank throws. If I remember correctly the head might have to be shimmed to avoid contact with the piston crown due to its higher tdc travel. You could build a nice cammed 2mil over motor that would give you great bang for your buck or go hog wild with big everything complete with "sick" power but you might have to freshen the top and bottom on a regular basis. Just my 2 cents
Last edited by beenthere; 01-18-2010 at 10:18 PM.