Thought i had something laying around in all my stuff.Think this might be what your looking for.If your bore is 1.5 inches,heres what i came up with:
1.5 inch=40mm
20mmx20mm(40mmsquared)x(PI-3.14)=1256
1256x a stroke of 32mm =40.1ccs
the specs on the engine in pic say39.7cc(2.42ci)---3.2hp@8000
18x10-prop7350
20x8prop-7500
22x8prop-7000
look at the specs in lower right hand corner and left lower corner,3 rings,theres no date on this flyer.says($189.95 on prepaid orders,we pay shipping.)this is a brand new 6 bolt hub never mounted.you can see in the pic the prop washer has a raised stem that is tapped for a spinner bolt. the 6 bolts for the prop are brand new i bought from ace a while back.the crankshaft thread is either 10mm or 7/16 i believe.hub is 1-1.2 long x1-5/8 diameter.send me a PM if interested.