MadBill wrote:Are you sure? How much radial P/V clearance is there? In the pix of the piston domes, it looks like both show radial witness marks in the left side (exhaust?) reliefs. The lower piston seems to show a single contact arc just below the top of the cutout at the 9:00 o' clock location and the upper one appears to have two short ones right on the top of the relief at say 8:00 and 10:00...
Also, not meaning to pile on, but there seem to be a number of very sharp edges and thin sections around the reliefs that could contribute to preignition.
No valve contact or close to contact...I leave the sharp edges...My bike goes faster that the bikes with radius edges, you just revealed my speed secret ...Build one of these old heaps and see if yours goes faster than mine...
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
...Build one of these old heaps and see if yours goes faster than mine... 
